*Corresponding Author: Gopal Anapana Assistant Professor, Department of Zoology, Maharajah’s
College Autonomous, Vizianagaram, Andhra Pradesh, India, Email: [email protected]. 89
International Journal of Zoology and Applied Biosciences ISSN: 2455-9571
Volume 10, Issue 5, pp: 89-96, 2025 http://www.ijzab.com
https://doi.org/10.55126/ijzab.2025.v10.i05.012
Research Article
DIVERSITY AND FUNCTIONAL MORPHOLOGY OF BIRD CLAWS IN THE
SRIKAKULAM REGION, ANDHRA PRADESH, INDIA
*Gopal Anapana, 1Lakshminarayana V and 2Venkata Rathnamma V
* Department of Zoology, Maharajah’s College Autonomous, Vizianagaram, Andhra Pradesh, India.
1Department of Botany, Maharajah’s College Autonomous, Vizianagaram, Andhra Pradesh, India.
2Department of Zoology & Aquaculture, Acharya Nagarjuna University, Guntur, Andhra Pradesh, India
Article History: Received 23rd July 2025; Accepted 9th September 2025; Published 30th September 2025
ABSTRACT
Avian claw morphology provides vital information on ecological adaptations related to locomotion, foraging strategies,
and habitat specialization. This study offers a comprehensive field-based survey of bird claw diversity across the
heterogeneous landscapes of Srikakulam District, Andhra Pradesh, India, conducted during the post monsoon period (June
to December 2024). We recorded 74 bird species spanning wetlands, forests, agricultural fields, and urban environments,
using direct observations complemented by high resolution photography. Species were classified into nine functional claw
types based on curvature, toe arrangement, and substrate interaction. Perching claws dominated (29.7%), followed by
wading, swimming, and raptorial forms. Strong associations emerged between claw morphology and habitat use,
reinforcing established functional adaptation frameworks. These results contribute valuable insights into avian
ecomorphology within tropical ecotones and establish a critical baseline for future conservation driven morphological and
behavioural research in the biologically rich yet understudied eastern peninsular region of India.
Keywords: Avian claw morphology, Functional adaptation, Habitat specialization, Srikakulam birds.
INTRODUCTION
The remarkable diversity in avian claw morphology reflects
the interplay of ecological niche specialization, behavioural
adaptation, and evolutionary history across bird lineages.
Composed primarily of keratin over a bony core, claws
fulfil essential functions including climbing, perching, prey
capture, swimming, and grooming, making them critical
indicators of both survival strategies and habitat
relationships throughout the avian class. Key
morphological aspects such as claw curvature, length-to-
width ratio, and cross-sectional structure have emerged as
reliable predictors of ecological roles and behavioural
repertoires among birds (Thomson & Motani, 2023;
Hedrick et al., 2019).
Avian claw shape has been repeatedly shown to correlate
with ecological demands and behaviour. Raptors such as
eagles and falcons possess robust, sharply curved talons for
prey immobilization, while perching birds exhibit
moderately curved claws that provide stability on branches
(Birn-Jeffery et al., 2012; Thomson & Motani, 2021).
Ground-dwelling species like pheasants show relatively
straight claws adapted for terrestrial traction, whereas
climbing birds such as woodpeckers display pronounced
curvature and asymmetry that enable adherence to vertical
substrates (Pintore et al., 2023). Aquatic species often
exhibit flattened or modified claw structures that aid
propulsion and manoeuvrability (Greenwold et al., 2014;
Carril et al., 2024). Comparative analyses further highlight
how claw form integrates with feeding, locomotion, and
grasping strategies, reflecting a balance between ecological
specialization and evolutionary constraints (Sustaita et al.,
2013; Martin & Sherratt, 2023).
Recent morphometric and biomechanical studies
underscore the importance of standardizing measurements
when interpreting ecological roles, as claw morphology can
vary substantially within taxa (Tinius & Russell, 2017).
Moreover, 3D modelling approaches reveal that the keratin
sheath responds dynamically to ecological pressures, while
the bony core retains phylogenetic signals, providing
Gopal Anapana et al. Int. J. Zool. Appl. Biosci., 10(5), 89-96, 2025
www.ijzab.com 90
palaeontologists with valuable insights into extinct taxa
(Hedrick et al., 2019; Carril et al., 2024). This duality
illustrates how claw morphology integrates functional
adaptation with evolutionary history. Habitat-specific
studies also confirm strong links between claw form and
substrate use, with tropical understorey birds showing
highly recurved claws for vertical perching, and open-
habitat species displaying broader, flatter claws for balance
on varied surfaces (Siri et al., 2020; Pintore et al., 2023).
While global research has advanced understanding of
avian ecomorphology, there remains a paucity of detailed
surveys focusing on the functional diversity of bird claws
within tropical and subtropical regions, particularly in
eastern India. The Srikakulam district of Andhra Pradesh,
positioned between the Eastern Ghats and the Bay of
Bengal, encompasses a mosaic of riverine, wetland, forest,
and agricultural habitats that support rich avifaunal
diversity. Yet, systematic documentation and analysis of
claw types, with emphasis on habitat, behaviour, and
conservation value, are notably lacking.
This study addresses this gap by systematically
categorizing and analysing avian claw diversity in the
Srikakulam region. It links claw morphology with habitat
use, feeding strategies, and ecological adaptation across
local bird communities, utilizing direct field observations
and photographic documentation. By highlighting patterns
of claw specialization and abundance, the research aims to
inform conservation efforts, raise regional awareness, and
contribute to the broader discourse on avian functional
morphology and adaptation.
Figure 1. India-Andhra Pradesh-Srikakulam.
MATERIALS AND METHODS
Study Area
The study was conducted in Srikakulam District, located in
the northeastern part of Andhra Pradesh, India.
Geographically, the district spans between 18°20′N to
19°10′N latitude and 83°25′E to 84°50′E longitude (Figure
1). Situated within a transitional zone between the Eastern
Ghats and the coastal plains of the Bay of Bengal,
Srikakulam exhibits remarkable ecological diversity and
supports a rich avifaunal community. Five major rivers
Vamshadhara, Nagavali, Suvarnamukhi, Mahendratanaya,
and Bahuda, originate in the Eastern Ghats and flow
eastward across the plains before emptying into the Bay of
Bengal. These river systems are accompanied by an
extensive network of over 8,000 irrigation tanks,
replenished seasonally by rainfall and channel fed
irrigation. This intricate hydrological infrastructure creates
a mosaic of perennial and seasonal aquatic habitats integral
to bird diversity in the region.
Study Period and Site Selection
Fieldwork for this study was conducted from June to
December 2024, covering the late pre-monsoon, monsoon,
and post-monsoon seasons in the Srikakulam region.
Surveys spanned diverse habitat types within Srikakulam
District, including wetlands, forest patches, agricultural
lands, riverbanks, and coastal stretches, selected based on
bird abundance, habitat diversity, and accessibility to
encompass a full range of ecological niches.
Sampling Method
Birds were recorded through a combination of systematic
transect walks and point counts across representative
habitats. Transects of 1–2km were established in forest
edge, wetland, and urban locations, with observers moving
slowly and noting all visually or aurally detected bird
species. Stationary point counts of 10-minute intervals were
deployed in marshes and dense vegetation, where visibility
was limited. Additional opportunistic observations outside
primary sampling hours further enriched the species list.
Bird Observation and Photography
Bird species were identified and documented using a Nikon
D3500 DSLR camera with a 70–300mm telephoto lens,
enabling clear visualization of foot and claw structures.
Observations were conducted during early morning (06:00–
09:30 hrs) and late afternoon (15:30–17:30 hrs), coinciding
www.ijzab.com 90
palaeontologists with valuable insights into extinct taxa
(Hedrick et al., 2019; Carril et al., 2024). This duality
illustrates how claw morphology integrates functional
adaptation with evolutionary history. Habitat-specific
studies also confirm strong links between claw form and
substrate use, with tropical understorey birds showing
highly recurved claws for vertical perching, and open-
habitat species displaying broader, flatter claws for balance
on varied surfaces (Siri et al., 2020; Pintore et al., 2023).
While global research has advanced understanding of
avian ecomorphology, there remains a paucity of detailed
surveys focusing on the functional diversity of bird claws
within tropical and subtropical regions, particularly in
eastern India. The Srikakulam district of Andhra Pradesh,
positioned between the Eastern Ghats and the Bay of
Bengal, encompasses a mosaic of riverine, wetland, forest,
and agricultural habitats that support rich avifaunal
diversity. Yet, systematic documentation and analysis of
claw types, with emphasis on habitat, behaviour, and
conservation value, are notably lacking.
This study addresses this gap by systematically
categorizing and analysing avian claw diversity in the
Srikakulam region. It links claw morphology with habitat
use, feeding strategies, and ecological adaptation across
local bird communities, utilizing direct field observations
and photographic documentation. By highlighting patterns
of claw specialization and abundance, the research aims to
inform conservation efforts, raise regional awareness, and
contribute to the broader discourse on avian functional
morphology and adaptation.
Figure 1. India-Andhra Pradesh-Srikakulam.
MATERIALS AND METHODS
Study Area
The study was conducted in Srikakulam District, located in
the northeastern part of Andhra Pradesh, India.
Geographically, the district spans between 18°20′N to
19°10′N latitude and 83°25′E to 84°50′E longitude (Figure
1). Situated within a transitional zone between the Eastern
Ghats and the coastal plains of the Bay of Bengal,
Srikakulam exhibits remarkable ecological diversity and
supports a rich avifaunal community. Five major rivers
Vamshadhara, Nagavali, Suvarnamukhi, Mahendratanaya,
and Bahuda, originate in the Eastern Ghats and flow
eastward across the plains before emptying into the Bay of
Bengal. These river systems are accompanied by an
extensive network of over 8,000 irrigation tanks,
replenished seasonally by rainfall and channel fed
irrigation. This intricate hydrological infrastructure creates
a mosaic of perennial and seasonal aquatic habitats integral
to bird diversity in the region.
Study Period and Site Selection
Fieldwork for this study was conducted from June to
December 2024, covering the late pre-monsoon, monsoon,
and post-monsoon seasons in the Srikakulam region.
Surveys spanned diverse habitat types within Srikakulam
District, including wetlands, forest patches, agricultural
lands, riverbanks, and coastal stretches, selected based on
bird abundance, habitat diversity, and accessibility to
encompass a full range of ecological niches.
Sampling Method
Birds were recorded through a combination of systematic
transect walks and point counts across representative
habitats. Transects of 1–2km were established in forest
edge, wetland, and urban locations, with observers moving
slowly and noting all visually or aurally detected bird
species. Stationary point counts of 10-minute intervals were
deployed in marshes and dense vegetation, where visibility
was limited. Additional opportunistic observations outside
primary sampling hours further enriched the species list.
Bird Observation and Photography
Bird species were identified and documented using a Nikon
D3500 DSLR camera with a 70–300mm telephoto lens,
enabling clear visualization of foot and claw structures.
Observations were conducted during early morning (06:00–
09:30 hrs) and late afternoon (15:30–17:30 hrs), coinciding
Gopal Anapana et al. Int. J. Zool. Appl. Biosci., 10(5), 89-96, 2025
www.ijzab.com 91
with peak avian activity. Binoculars (8×42 and 10×50)
were used for close field observation, and targeted
photographs were taken for later examination of pedal
morphology, ensuring that ventral and lateral views of
claws were captured during perching, feeding, or flight.
Species Identification
Species identification followed standard field guidelines,
including: Ali, S. (2002). The Book of Indian Birds.
Bombay Natural History Society. Grimmett, R., Inskipp,
C., & Inskipp, T. (2011). Birds of the Indian Subcontinent.
Helm Field Guides. Scientific names and taxonomic
classifications were cross checked against the Bird Life
International database and IOC World Bird List v13.1 (Gill
et al., 2023).
Classification of Claw Types
Claw types were categorized primarily through direct field
observation of foraging birds, with behavioural clues such
as perching, climbing, wading, and swimming guiding
morphological assignment. Where possible, photographs
were taken for confirmation and measurement. For elusive
or less visible species, published literature and regional
field guides (e.g., Rasmussen & Anderton, 2012; Ali &
Ripley, 1987) supplemented and validated claw type
assignment. No museum specimens were examined as part
of this study. Functional claw categories were adapted from
current ecomorphological frameworks (Birn-Jeffery et al.,
2012; Hedrick et al., 2019), considering features such as
claw curvature, length to width ratio, digit arrangement
(e.g., Anisodactyl, Zygodactyl), and substrate interaction
behaviour. Each species was assigned to one of the
following types based on photographic analysis and field
observations (Table 3): Perching claws, grasping claws
(raptors), Climbing claws, wading claws, Ground foraging
claws, Scratching claws, Swimming claws, Clinging claws
(arboreal), Specialized claws (e.g., fish catchers, pectinate
for grooming).
Data Recording and Analysis
A total of 74 bird species representing multiple orders
(Passeriformes, Accipitriformes, Charadriiformes, etc.)
were recorded. For each species, data on claw morphology,
habitat type, and behavioural context were documented.
The photographic dataset was analysed using ImageJ
software to measure claw curvature (arc angle), total
length, and arc depth where possible. Associations between
claw type and habitat type were summarized in tabular
form. Data interpretation was primarily qualitative, with
plans for morphometric analysis in future studies.
Functional classification of avian claws and feet
The morphology of avian feet and claws reflects
evolutionary adaptations to ecological niches and
locomotor behaviours. On the basis of functional
characteristics, the observed bird species in the study area
could be broadly classified into the following claw foot
types:
Cursorial (Running) Feet
Cursorial birds, such as bustards and ostriches, possess
elongated and muscular legs adapted for terrestrial
locomotion. Typically, these species exhibit reduced digits;
the hind toe is diminished or absent, and the remaining
anterior toes are aligned forward to support fast running.
The ostrich (Struthio camelus) uniquely possesses only two
toes, with the larger inner toe bearing a nail for propulsion
(Ziswiler, 1965).
Perching Feet
Common among passerines (e.g., sparrows, bulbuls, robins,
and mynahs), perching feet results in three forward
pointing toes and a reversed hallux (hind toe), forming a
strong grip for securely clasping branches. This anisodactyl
arrangement allows dynamic stability during perching and
roosting.
Scratching Feet
As observed in birds such as fowl, quail, and pheasants,
these feet are robust, with thick claws and an emphasis on
ground interaction. Males often possess bony spurs on the
tarsus, which are used for both foraging and territorial
combat (Collias & Collias, 1967).
Raptorial Feet
Predatory species (e.g., eagles, hawks, owls, kites) exhibit
powerful, curved talons on all digits and are designed to
pierce, grasp, and immobilize prey. The presence of tylari
fleshy pads on the ventral side of toes enhances grip. In fish
eating raptors such as the osprey (Pandion haliaetus), sharp
keratinous spines replace tylari to prevent slippage during
prey capture (Hertel, 1995).
Wading Feet
Species such as herons, jacanas, and snipes display
elongated toes and legs adapted for navigating wetlands
and marshes. These feet are usually nonwebbed or slightly
webbed, allowing a balance between floating vegetation
and mudflats (Prum, 1990).
Swimming Feet
Aquatic birds are adapted for propulsion in water via
various foot modifications: Ducks and teals: possess
palmate feet (three front toes connected by full webbing).
Grebes and coots: Lobate feet, where each toe has a
separate skin flap, improving underwater thrust.
Cormorants and pelicans have totipalmate feet, with all
four toe webbeds (Livezey, 1990).
Climbing Feet
Seen in parrots and woodpeckers, these feet are
zygodactylous, with two toes facing forward and two
facing backwards, enhancing the vertical grip and
manipulation of surfaces or food.
www.ijzab.com 91
with peak avian activity. Binoculars (8×42 and 10×50)
were used for close field observation, and targeted
photographs were taken for later examination of pedal
morphology, ensuring that ventral and lateral views of
claws were captured during perching, feeding, or flight.
Species Identification
Species identification followed standard field guidelines,
including: Ali, S. (2002). The Book of Indian Birds.
Bombay Natural History Society. Grimmett, R., Inskipp,
C., & Inskipp, T. (2011). Birds of the Indian Subcontinent.
Helm Field Guides. Scientific names and taxonomic
classifications were cross checked against the Bird Life
International database and IOC World Bird List v13.1 (Gill
et al., 2023).
Classification of Claw Types
Claw types were categorized primarily through direct field
observation of foraging birds, with behavioural clues such
as perching, climbing, wading, and swimming guiding
morphological assignment. Where possible, photographs
were taken for confirmation and measurement. For elusive
or less visible species, published literature and regional
field guides (e.g., Rasmussen & Anderton, 2012; Ali &
Ripley, 1987) supplemented and validated claw type
assignment. No museum specimens were examined as part
of this study. Functional claw categories were adapted from
current ecomorphological frameworks (Birn-Jeffery et al.,
2012; Hedrick et al., 2019), considering features such as
claw curvature, length to width ratio, digit arrangement
(e.g., Anisodactyl, Zygodactyl), and substrate interaction
behaviour. Each species was assigned to one of the
following types based on photographic analysis and field
observations (Table 3): Perching claws, grasping claws
(raptors), Climbing claws, wading claws, Ground foraging
claws, Scratching claws, Swimming claws, Clinging claws
(arboreal), Specialized claws (e.g., fish catchers, pectinate
for grooming).
Data Recording and Analysis
A total of 74 bird species representing multiple orders
(Passeriformes, Accipitriformes, Charadriiformes, etc.)
were recorded. For each species, data on claw morphology,
habitat type, and behavioural context were documented.
The photographic dataset was analysed using ImageJ
software to measure claw curvature (arc angle), total
length, and arc depth where possible. Associations between
claw type and habitat type were summarized in tabular
form. Data interpretation was primarily qualitative, with
plans for morphometric analysis in future studies.
Functional classification of avian claws and feet
The morphology of avian feet and claws reflects
evolutionary adaptations to ecological niches and
locomotor behaviours. On the basis of functional
characteristics, the observed bird species in the study area
could be broadly classified into the following claw foot
types:
Cursorial (Running) Feet
Cursorial birds, such as bustards and ostriches, possess
elongated and muscular legs adapted for terrestrial
locomotion. Typically, these species exhibit reduced digits;
the hind toe is diminished or absent, and the remaining
anterior toes are aligned forward to support fast running.
The ostrich (Struthio camelus) uniquely possesses only two
toes, with the larger inner toe bearing a nail for propulsion
(Ziswiler, 1965).
Perching Feet
Common among passerines (e.g., sparrows, bulbuls, robins,
and mynahs), perching feet results in three forward
pointing toes and a reversed hallux (hind toe), forming a
strong grip for securely clasping branches. This anisodactyl
arrangement allows dynamic stability during perching and
roosting.
Scratching Feet
As observed in birds such as fowl, quail, and pheasants,
these feet are robust, with thick claws and an emphasis on
ground interaction. Males often possess bony spurs on the
tarsus, which are used for both foraging and territorial
combat (Collias & Collias, 1967).
Raptorial Feet
Predatory species (e.g., eagles, hawks, owls, kites) exhibit
powerful, curved talons on all digits and are designed to
pierce, grasp, and immobilize prey. The presence of tylari
fleshy pads on the ventral side of toes enhances grip. In fish
eating raptors such as the osprey (Pandion haliaetus), sharp
keratinous spines replace tylari to prevent slippage during
prey capture (Hertel, 1995).
Wading Feet
Species such as herons, jacanas, and snipes display
elongated toes and legs adapted for navigating wetlands
and marshes. These feet are usually nonwebbed or slightly
webbed, allowing a balance between floating vegetation
and mudflats (Prum, 1990).
Swimming Feet
Aquatic birds are adapted for propulsion in water via
various foot modifications: Ducks and teals: possess
palmate feet (three front toes connected by full webbing).
Grebes and coots: Lobate feet, where each toe has a
separate skin flap, improving underwater thrust.
Cormorants and pelicans have totipalmate feet, with all
four toe webbeds (Livezey, 1990).
Climbing Feet
Seen in parrots and woodpeckers, these feet are
zygodactylous, with two toes facing forward and two
facing backwards, enhancing the vertical grip and
manipulation of surfaces or food.
Gopal Anapana et al. Int. J. Zool. Appl. Biosci., 10(5), 89-96, 2025
www.ijzab.com 92
Clinging Feet
Birds such as swifts and hummingbirds exhibit
pamprodactylous feet all four toes directed forward
allowing them to cling to vertical surfaces such as cliffs or
manmade structures. This unique configuration supports
hovering or inverted rest (Collins, 2004).
Specialized Modifications
Some species present unique claw traits: Poorwill
(Phalaenoptilus nuttallii) has a pectinate (comb like) claw
used for grooming rich bristles. Ruffed grouse develops
seasonal toe fringes (dermal expansions) that improve
mobility over snow, akin to snowshoes. Larks exhibit
elongated hind claws, possibly aiding in perching on flat,
open terrain.
RESULTS AND DISCUSSION
A total of 74 bird species representing diverse avian
families were recorded across a variety of habitats in
Srikakulam District during the survey period from June to
December 2024. These habitats included wetlands, forests,
agricultural fields, and urban areas. Considerable variation
in claw morphology was observed, allowing classification
into nine distinct functional claw types linked to ecological
roles. The distribution of species among claw types is
summarized in Table 1 & Figure 2. Perching claws were
the most common, followed by wading and swimming
adaptations. The diversity of claw morphologies reflects
functional adaptations to habitat specialization and
behavioural needs (Figure 3).
Table 1. Perching claws were the most common, followed by wading and swimming adaptations.
Claw Type No. of Species (n=74) Percent (%)
Perching 22 29.7%
Wading 14 18.9%
Swimming 10 13.5%
Scratching 8 10.8%
Climbing 6 8.1%
Raptorial 7 9.5%
Other (Specialized)* 7 9.5%
*Includes clinging feet, seasonal adaptations, and pectinate claws.
Figure 2. Pie chart illustrating the proportional distribution of claw types among the 74 species surveyed.
Claw types exhibited clear relationships with habitat preferences: Wetland species: Predominantly showed wading and
swimming claws, facilitating navigation of marshes, mudflats, and water bodies. Urban and edge-dwelling birds: Exhibited
primarily perching claws, supporting arboreal and substrate grasping in human modified landscapes. Forest species:
Demonstrated raptorial claws (in raptors) and climbing claws (woodpeckers, parrots), reflecting adaptations to arboreal
predation and locomotion.
www.ijzab.com 92
Clinging Feet
Birds such as swifts and hummingbirds exhibit
pamprodactylous feet all four toes directed forward
allowing them to cling to vertical surfaces such as cliffs or
manmade structures. This unique configuration supports
hovering or inverted rest (Collins, 2004).
Specialized Modifications
Some species present unique claw traits: Poorwill
(Phalaenoptilus nuttallii) has a pectinate (comb like) claw
used for grooming rich bristles. Ruffed grouse develops
seasonal toe fringes (dermal expansions) that improve
mobility over snow, akin to snowshoes. Larks exhibit
elongated hind claws, possibly aiding in perching on flat,
open terrain.
RESULTS AND DISCUSSION
A total of 74 bird species representing diverse avian
families were recorded across a variety of habitats in
Srikakulam District during the survey period from June to
December 2024. These habitats included wetlands, forests,
agricultural fields, and urban areas. Considerable variation
in claw morphology was observed, allowing classification
into nine distinct functional claw types linked to ecological
roles. The distribution of species among claw types is
summarized in Table 1 & Figure 2. Perching claws were
the most common, followed by wading and swimming
adaptations. The diversity of claw morphologies reflects
functional adaptations to habitat specialization and
behavioural needs (Figure 3).
Table 1. Perching claws were the most common, followed by wading and swimming adaptations.
Claw Type No. of Species (n=74) Percent (%)
Perching 22 29.7%
Wading 14 18.9%
Swimming 10 13.5%
Scratching 8 10.8%
Climbing 6 8.1%
Raptorial 7 9.5%
Other (Specialized)* 7 9.5%
*Includes clinging feet, seasonal adaptations, and pectinate claws.
Figure 2. Pie chart illustrating the proportional distribution of claw types among the 74 species surveyed.
Claw types exhibited clear relationships with habitat preferences: Wetland species: Predominantly showed wading and
swimming claws, facilitating navigation of marshes, mudflats, and water bodies. Urban and edge-dwelling birds: Exhibited
primarily perching claws, supporting arboreal and substrate grasping in human modified landscapes. Forest species:
Demonstrated raptorial claws (in raptors) and climbing claws (woodpeckers, parrots), reflecting adaptations to arboreal
predation and locomotion.
Gopal Anapana et al. Int. J. Zool. Appl. Biosci., 10(5), 89-96, 2025
www.ijzab.com 93
Figure 3. Bar chart showing the frequency of claw types across major habitat categories: Wetland, Forest, Urban,
Agricultural.
Table 2. Detailed field observations enabled classification of claw types in commonly encountered species, combining
ecological context with morphology.
S. No Common Name Scientific Name Claw Type Habitat Type
1 Indian Peafowl Pavo cristatus Scratching Forest Edge
2 House Sparrow Passer domesticus Perching Wetland Edge
3 Grey headed Swamphen Porphyrio poliocephalus Climbing Wetland
4 White throated Kingfisher Halcyon smyrnensis Perching Freshwater Marsh
5 Indian Pond Heron Ardeola grayii Wading Freshwater Marsh
6 Rose ringed Parakeet Psittacula krameri Climbing Urban
7 Common Myna Acridotheres tristis Perching Forest Edge
8 House Sparrow Passer domesticus Perching Freshwater Marsh
9 Little Cormorant Microcarbo niger Swimming Wetland
10 White throated Kingfisher Halcyon smyrnensis Perching Wetland Edge
Indian Peafowl (Pavo cristatus): Displays scratching claws
ideal for terrestrial foraging and roosting. House Sparrow
(Passer domesticus): Classic perching feet conducive to
branch grasping in urban/agricultural habitats. Grey headed
Swamphen (Porphyrio poliocephalus): Adapted climbing
claws for dense wetland vegetation. White throated
Kingfisher (Halcyon smyrnensis): Perching claws suited for
grasping exposed perches near water. Indian Pond Heron
(Ardeola grayii): Wading feet optimized for marshy
habitats. Rose ringed Parakeet (Psittacula krameri): Curved
claws enabling arboreal climbing. Common Myna
(Acridotheres tristis): Versatile perching claws enabling
urban adaptability. Little Cormorant (Microcarbo niger):
Swimming feet with webbing aiding aquatic propulsion.
The present study provides a comprehensive analysis of
avian claw morphology linked with habitat utilization
across 74 bird species in the ecologically diverse
Srikakulam District, Andhra Pradesh. The observed
diversity of claw types from perching and wading to
raptorial and climbing reflects clear functional adaptations
consistent with global avian ecomorphological patterns and
underscores the intricate relationship between morphology,
behaviour, and environment. The predominance of
perching claws (29.7%) in our dataset aligns well with
global data indicating that passerines with anisodactyl foot
arrangements dominate many terrestrial bird communities
(Martin & Sherratt, 2023). This prevalence illustrates the
versatility of perching adaptations, facilitating arboreal
locomotion and the exploitation of a broad range of
habitats, including rapidly changing urban agroforestry
landscapes. However, continued urban expansion and
habitat fragmentation in the region pose risks by potentially
reducing adequate perching substrates, which could
negatively impact these species (Figure 3).
www.ijzab.com 93
Figure 3. Bar chart showing the frequency of claw types across major habitat categories: Wetland, Forest, Urban,
Agricultural.
Table 2. Detailed field observations enabled classification of claw types in commonly encountered species, combining
ecological context with morphology.
S. No Common Name Scientific Name Claw Type Habitat Type
1 Indian Peafowl Pavo cristatus Scratching Forest Edge
2 House Sparrow Passer domesticus Perching Wetland Edge
3 Grey headed Swamphen Porphyrio poliocephalus Climbing Wetland
4 White throated Kingfisher Halcyon smyrnensis Perching Freshwater Marsh
5 Indian Pond Heron Ardeola grayii Wading Freshwater Marsh
6 Rose ringed Parakeet Psittacula krameri Climbing Urban
7 Common Myna Acridotheres tristis Perching Forest Edge
8 House Sparrow Passer domesticus Perching Freshwater Marsh
9 Little Cormorant Microcarbo niger Swimming Wetland
10 White throated Kingfisher Halcyon smyrnensis Perching Wetland Edge
Indian Peafowl (Pavo cristatus): Displays scratching claws
ideal for terrestrial foraging and roosting. House Sparrow
(Passer domesticus): Classic perching feet conducive to
branch grasping in urban/agricultural habitats. Grey headed
Swamphen (Porphyrio poliocephalus): Adapted climbing
claws for dense wetland vegetation. White throated
Kingfisher (Halcyon smyrnensis): Perching claws suited for
grasping exposed perches near water. Indian Pond Heron
(Ardeola grayii): Wading feet optimized for marshy
habitats. Rose ringed Parakeet (Psittacula krameri): Curved
claws enabling arboreal climbing. Common Myna
(Acridotheres tristis): Versatile perching claws enabling
urban adaptability. Little Cormorant (Microcarbo niger):
Swimming feet with webbing aiding aquatic propulsion.
The present study provides a comprehensive analysis of
avian claw morphology linked with habitat utilization
across 74 bird species in the ecologically diverse
Srikakulam District, Andhra Pradesh. The observed
diversity of claw types from perching and wading to
raptorial and climbing reflects clear functional adaptations
consistent with global avian ecomorphological patterns and
underscores the intricate relationship between morphology,
behaviour, and environment. The predominance of
perching claws (29.7%) in our dataset aligns well with
global data indicating that passerines with anisodactyl foot
arrangements dominate many terrestrial bird communities
(Martin & Sherratt, 2023). This prevalence illustrates the
versatility of perching adaptations, facilitating arboreal
locomotion and the exploitation of a broad range of
habitats, including rapidly changing urban agroforestry
landscapes. However, continued urban expansion and
habitat fragmentation in the region pose risks by potentially
reducing adequate perching substrates, which could
negatively impact these species (Figure 3).
Gopal Anapana et al. Int. J. Zool. Appl. Biosci., 10(5), 89-96, 2025
www.ijzab.com 94
Wading claws, comprising 18.9% of species, were
strongly associated with wetland habitats, especially herons
and moorhens. Their elongated toes allow weight
distribution over unstable substrates, which is pivotal for
survival amid mounting hydrological stresses from altered
water regimes and wetland degradation (De Mendoza et al.,
2024). The conservation of wetland integrity is thus
essential to maintain the ecological functions supported by
such specialized morphologies. Swimming claws,
accounting for 13.5%, correspond with Srikakulam’s
network of tanks and reservoirs, supporting water adapted
species like cormorants and coots. Their palmate and
totipalmate feet exemplify morphological trade-offs:
optimized for aquatic propulsion but less efficient on land
(Tyler, 2023). These adaptations highlight the need to
safeguard aquatic habitats not just for bird abundance but
for maintaining functional biodiversity.
The allocation of claw designs in scratching birds such as
Galliformes, climbing species within Psittaciformes, and
the raptorial curvature in Accipitriformes supports the idea
of morphological modularity and niche partitioning seen
worldwide (Kerschbaumer & Pfingstl, 2024). Raptors
like Milvus migrans employ hypertrophied talons and
specialized pads (tylari or spicules) to immobilize prey,
illustrating a convergence of predatory adaptations across
taxa. The less common but no less significant category of
clinging and specialized claws (9.5%) reveals behavioural
and structural innovation shaped by ecological demands.
Notably, the pectinate claws of certain nightjars and
grooming specialized claws in ground foraging larks
provide examples of nonlocomotory functions of claws,
emphasizing the multidimensional roles of pedal
morphology, often overlooked in ecological surveys
(Orkney et al., 2025). These specialized forms highlight
evolutionary responses to unique ecological pressures and
contribute to the morpho functional diversity within bird
communities. Srikakulam’s position as an ecotone between
the Eastern Ghats uplands and Bay of Bengal coastal plains
offers a distinctive biogeographic framework to examine
adaptive radiation. The co-occurrence of forest associated
birds with climbing and scratching claws alongside aquatic
birds with wading and swimming adaptations suggests
morphological convergence driven by diverse ecological
opportunities a pattern reminiscent of adaptive radiations in
Neotropical avifaunas (Claramunt et al., 2023). Moreover,
the spatial and seasonal overlap of multiple species with
differing claw morphologies may promote niche
partitioning, reduce interspecific competition and facilitate
coexistence through functional divergence. These findings
corroborate recent research positing that habitat structure
predicts claw morphologies more robustly than taxonomy
alone (Picasso et al., 2025), underscoring the power of
environmental filters in shaping morphological diversity.
This study is observational in nature and subject to the
constraints of field-based identification and photographic
documentation. The sample size, representing 74 species,
limits comprehensive coverage of the region’s avifauna,
especially rare or seasonally migratory taxa. Quantitative
morphometric analysis (e.g., measurements of claw
curvature, length, and arc) was not performed, but could
provide deeper insights into functional variation in future
studies. Additionally, potential observer bias and sampling
gaps may influence the representativeness of claw type
prevalence. The diversity and prevalence of specific claw
types reflect the distribution and health of corresponding
habitats. For instance, declines in wading birds identified
by specialized elongated claws could indicate wetland
degradation or water regime changes. The presence or
absence of swimming and perching claw types in urban or
agricultural landscapes may serve as ecological indicators
for habitat integrity and suitability for specialist and
generalist birds. Monitoring claw type assemblages thus
provides an indirect, but effective, tool for ecosystem
health assessment and prioritization of conservation action.
To further understand the evolutionary and ecological
dynamics of avian claw morphology, integrative
approaches are recommended. Future studies should
combine detailed morphometric measurements using
geometric morphometrics with molecular phylogenetic
analyses to distinguish between adaptive convergence and
inherited traits. Long term ecological monitoring, including
the impacts of climate change on habitat distribution and
bird communities, would be valuable. Linking claw
morphology datasets with climate, land use change, and
population trends could help predict shifts in functional
adaptation and inform proactive conservation strategies.
CONCLUSION
This study presents one of the first comprehensive
assessments of avian claw diversity in the Srikakulam
District, documenting 74 bird species and categorizing their
claws into nine distinct functional types. The findings
reveal a robust link between claw morphology and habitat
specialization, affirming established ecological and
evolutionary principles. The dominance of perching claws
among urban and edge species, coupled with the clear
association of wading and swimming claws with wetland
habitats, reinforces the role of foot structure as a reliable
indicator of ecological behaviour and niche adaptation.
Moreover, the discovery of specialized claw forms such as
raptorial, clinging, and pectinate types highlights the
evolutionary flexibility of avian morphology in response to
environmental challenges and opportunities. Situated at the
confluence of the Eastern Ghats and coastal plains, the
Srikakulam region’s complex habitats and rich bird
diversity provide an invaluable natural laboratory to
explore adaptive radiation and niche differentiation. This
baseline dataset lays the groundwork for future
morphometric, behavioural, and conservation focused
research, which is critical in the face of accelerating habitat
degradation and climate change. To further elucidate the
intricate links between morphology and function,
integrative studies involving detailed morphometrics,
biomechanical analyses, and ecological modelling are
strongly encouraged, especially for rapidly changing
ecosystems across South Asia.
www.ijzab.com 94
Wading claws, comprising 18.9% of species, were
strongly associated with wetland habitats, especially herons
and moorhens. Their elongated toes allow weight
distribution over unstable substrates, which is pivotal for
survival amid mounting hydrological stresses from altered
water regimes and wetland degradation (De Mendoza et al.,
2024). The conservation of wetland integrity is thus
essential to maintain the ecological functions supported by
such specialized morphologies. Swimming claws,
accounting for 13.5%, correspond with Srikakulam’s
network of tanks and reservoirs, supporting water adapted
species like cormorants and coots. Their palmate and
totipalmate feet exemplify morphological trade-offs:
optimized for aquatic propulsion but less efficient on land
(Tyler, 2023). These adaptations highlight the need to
safeguard aquatic habitats not just for bird abundance but
for maintaining functional biodiversity.
The allocation of claw designs in scratching birds such as
Galliformes, climbing species within Psittaciformes, and
the raptorial curvature in Accipitriformes supports the idea
of morphological modularity and niche partitioning seen
worldwide (Kerschbaumer & Pfingstl, 2024). Raptors
like Milvus migrans employ hypertrophied talons and
specialized pads (tylari or spicules) to immobilize prey,
illustrating a convergence of predatory adaptations across
taxa. The less common but no less significant category of
clinging and specialized claws (9.5%) reveals behavioural
and structural innovation shaped by ecological demands.
Notably, the pectinate claws of certain nightjars and
grooming specialized claws in ground foraging larks
provide examples of nonlocomotory functions of claws,
emphasizing the multidimensional roles of pedal
morphology, often overlooked in ecological surveys
(Orkney et al., 2025). These specialized forms highlight
evolutionary responses to unique ecological pressures and
contribute to the morpho functional diversity within bird
communities. Srikakulam’s position as an ecotone between
the Eastern Ghats uplands and Bay of Bengal coastal plains
offers a distinctive biogeographic framework to examine
adaptive radiation. The co-occurrence of forest associated
birds with climbing and scratching claws alongside aquatic
birds with wading and swimming adaptations suggests
morphological convergence driven by diverse ecological
opportunities a pattern reminiscent of adaptive radiations in
Neotropical avifaunas (Claramunt et al., 2023). Moreover,
the spatial and seasonal overlap of multiple species with
differing claw morphologies may promote niche
partitioning, reduce interspecific competition and facilitate
coexistence through functional divergence. These findings
corroborate recent research positing that habitat structure
predicts claw morphologies more robustly than taxonomy
alone (Picasso et al., 2025), underscoring the power of
environmental filters in shaping morphological diversity.
This study is observational in nature and subject to the
constraints of field-based identification and photographic
documentation. The sample size, representing 74 species,
limits comprehensive coverage of the region’s avifauna,
especially rare or seasonally migratory taxa. Quantitative
morphometric analysis (e.g., measurements of claw
curvature, length, and arc) was not performed, but could
provide deeper insights into functional variation in future
studies. Additionally, potential observer bias and sampling
gaps may influence the representativeness of claw type
prevalence. The diversity and prevalence of specific claw
types reflect the distribution and health of corresponding
habitats. For instance, declines in wading birds identified
by specialized elongated claws could indicate wetland
degradation or water regime changes. The presence or
absence of swimming and perching claw types in urban or
agricultural landscapes may serve as ecological indicators
for habitat integrity and suitability for specialist and
generalist birds. Monitoring claw type assemblages thus
provides an indirect, but effective, tool for ecosystem
health assessment and prioritization of conservation action.
To further understand the evolutionary and ecological
dynamics of avian claw morphology, integrative
approaches are recommended. Future studies should
combine detailed morphometric measurements using
geometric morphometrics with molecular phylogenetic
analyses to distinguish between adaptive convergence and
inherited traits. Long term ecological monitoring, including
the impacts of climate change on habitat distribution and
bird communities, would be valuable. Linking claw
morphology datasets with climate, land use change, and
population trends could help predict shifts in functional
adaptation and inform proactive conservation strategies.
CONCLUSION
This study presents one of the first comprehensive
assessments of avian claw diversity in the Srikakulam
District, documenting 74 bird species and categorizing their
claws into nine distinct functional types. The findings
reveal a robust link between claw morphology and habitat
specialization, affirming established ecological and
evolutionary principles. The dominance of perching claws
among urban and edge species, coupled with the clear
association of wading and swimming claws with wetland
habitats, reinforces the role of foot structure as a reliable
indicator of ecological behaviour and niche adaptation.
Moreover, the discovery of specialized claw forms such as
raptorial, clinging, and pectinate types highlights the
evolutionary flexibility of avian morphology in response to
environmental challenges and opportunities. Situated at the
confluence of the Eastern Ghats and coastal plains, the
Srikakulam region’s complex habitats and rich bird
diversity provide an invaluable natural laboratory to
explore adaptive radiation and niche differentiation. This
baseline dataset lays the groundwork for future
morphometric, behavioural, and conservation focused
research, which is critical in the face of accelerating habitat
degradation and climate change. To further elucidate the
intricate links between morphology and function,
integrative studies involving detailed morphometrics,
biomechanical analyses, and ecological modelling are
strongly encouraged, especially for rapidly changing
ecosystems across South Asia.
Gopal Anapana et al. Int. J. Zool. Appl. Biosci., 10(5), 89-96, 2025
www.ijzab.com 95
ACKNOWLEDGMENT
The authors express their sincere gratitude to the local
communities and individuals in Srikakulam District who
provided valuable support during fieldwork and data
collection
CONFLICT OF INTERESTS
The authors declare no conflict of interest
ETHICS APPROVAL
Not applicable
FUNDING
This study received no specific funding from public,
commercial, or not-for-profit funding agencies.
AI TOOL DECLARATION
The authors declares that no AI and related tools are used to
write the scientific content of this manuscript.
DATA AVAILABILITY
Data will be available on request
REFERENCES
Ali, S. (2002). The book of Indian birds. Bombay Natural
History Society.
Ali, S., & Ripley, S. D. (1987). Compact handbook of the
birds of India and Pakistan: Together with those of
Bangladesh, Nepal, Bhutan and Sri Lanka (2nd ed.).
Oxford University Press.
Birn-Jeffery, A. V., Miller, S., Naish, D., Codd, J. R., &
Sellers, W. I. (2012). Pedal claw curvature in birds,
lizards and Mesozoic dinosaurs. PLOS ONE, 7(12),
e50555. https://doi.org/10.1371/journal.pone.0050555
Carril, J., et al. (2024). Evolution of avian foot morphology
through anatomical network analysis. Nature
Communications.
https://www.nature.com/articles/s41467-024-54297-9
Claramunt, S., & Derryberry, E. P. (2023). Climbing
adaptations and cladogenesis in the Furnariidae.
American Naturalist.
Collias, N. E., & Collias, E. C. (1967). A review of the
nesting habits and nest structures of the Old World
weaverbirds. In Proceedings of the International
Ornithological Congress, Helsinki, 1966 (pp. 168–184).
Collins, C. T. (2004). The pamprodactyl foot of swifts: Its
use in vertical clinging and evolution in the Apodidae.
Bulletin of the British Ornithologists’ Club, 124(4), 255–
262.
De Mendoza, R., et al. (2024). The evolutionary journey of
the avian foot through its networks. ResearchGate.
Fabre, A. C., et al. (2017). Foot shape in arboreal birds:
Two morphological patterns for the same pincer‐like tool.
Journal of Anatomy, 230(6), 731–743.
https://doi.org/10.1111/joa.12614
Gill, F., Donsker, D., & Rasmussen, P. (Eds.). (2023). IOC
World Bird List (v13.1).
https://doi.org/10.14344/IOC.ML.13.1
Greenwold, M. J., et al. (2014). Dynamic evolution of
keratins in birds and their adaptation to novel lifestyles.
BMC Evolutionary Biology, 14, 249.
https://doi.org/10.1186/s12862-014-0249-1
Grimmett, R., Inskipp, C., & Inskipp, T. (2011). Birds of
the Indian subcontinent (Helm Field Guides).
Hedrick, B. P., Cordero, S. A., Zanno, L. E., & Noto, C.
(2019). Quantifying shape and ecology in avian pedal
claws: The relationship between the bony core and
keratinous sheath. Ecology and Evolution, 9(14), 8292–
8304. https://doi.org/10.1002/ece3.5507
Hertel, F. (1995). Ecomorphological indicators of feeding
behavior in recent and fossil raptors. Auk, 112(4), 890–
903.
Kerschbaumer, M., & Pfingstl, T. (2024). Multiple factors
influence claw characteristics in mites. Scientific Reports.
Livezey, B. C. (1990). Systematics and morphology of
grebes. Ornithological Monographs.
Martin, E. M., & Sherratt, E. (2023). Grasping hold of
functional trade-offs using the diversity of foot forms in
Australian birds. Evolutionary Ecology.
https://doi.org/10.1007/s10682-023-10261-5
Orkney, A., et al. (2025). Integration of forelimb and
hindlimb morphology in vertebrate evolution. Nature
Ecology & Evolution.
Picasso, M. B. J., et al. (2025). Hindlimb bone proportions
and prey preferences in owls. Zoological Journal of the
Linnean Society.
Pintore, R., et al. (2023). Foot adaptation to climbing in
ovenbirds and woodcreepers (Furnariida). Journal of
Anatomy, 243(4), 567–578.
Prum, R. O. (1990). Phylogenetic analysis of the evolution
of display behavior in the Neotropical manakins (Aves:
Pipridae). Ethology.
Rasmussen, P. C., & Anderton, J. C. (2012). Birds of South
Asia: The Ripley guide (2nd ed.). Lynx Edicions /
Smithsonian Institution.
Siri, S., Ponpituk, Y., Safoowong, M., Nuipakdee, W.,
Marod, D., & Duengkae, P. (2020). Comparing
morphological traits of legs of understory birds inhabiting
www.ijzab.com 95
ACKNOWLEDGMENT
The authors express their sincere gratitude to the local
communities and individuals in Srikakulam District who
provided valuable support during fieldwork and data
collection
CONFLICT OF INTERESTS
The authors declare no conflict of interest
ETHICS APPROVAL
Not applicable
FUNDING
This study received no specific funding from public,
commercial, or not-for-profit funding agencies.
AI TOOL DECLARATION
The authors declares that no AI and related tools are used to
write the scientific content of this manuscript.
DATA AVAILABILITY
Data will be available on request
REFERENCES
Ali, S. (2002). The book of Indian birds. Bombay Natural
History Society.
Ali, S., & Ripley, S. D. (1987). Compact handbook of the
birds of India and Pakistan: Together with those of
Bangladesh, Nepal, Bhutan and Sri Lanka (2nd ed.).
Oxford University Press.
Birn-Jeffery, A. V., Miller, S., Naish, D., Codd, J. R., &
Sellers, W. I. (2012). Pedal claw curvature in birds,
lizards and Mesozoic dinosaurs. PLOS ONE, 7(12),
e50555. https://doi.org/10.1371/journal.pone.0050555
Carril, J., et al. (2024). Evolution of avian foot morphology
through anatomical network analysis. Nature
Communications.
https://www.nature.com/articles/s41467-024-54297-9
Claramunt, S., & Derryberry, E. P. (2023). Climbing
adaptations and cladogenesis in the Furnariidae.
American Naturalist.
Collias, N. E., & Collias, E. C. (1967). A review of the
nesting habits and nest structures of the Old World
weaverbirds. In Proceedings of the International
Ornithological Congress, Helsinki, 1966 (pp. 168–184).
Collins, C. T. (2004). The pamprodactyl foot of swifts: Its
use in vertical clinging and evolution in the Apodidae.
Bulletin of the British Ornithologists’ Club, 124(4), 255–
262.
De Mendoza, R., et al. (2024). The evolutionary journey of
the avian foot through its networks. ResearchGate.
Fabre, A. C., et al. (2017). Foot shape in arboreal birds:
Two morphological patterns for the same pincer‐like tool.
Journal of Anatomy, 230(6), 731–743.
https://doi.org/10.1111/joa.12614
Gill, F., Donsker, D., & Rasmussen, P. (Eds.). (2023). IOC
World Bird List (v13.1).
https://doi.org/10.14344/IOC.ML.13.1
Greenwold, M. J., et al. (2014). Dynamic evolution of
keratins in birds and their adaptation to novel lifestyles.
BMC Evolutionary Biology, 14, 249.
https://doi.org/10.1186/s12862-014-0249-1
Grimmett, R., Inskipp, C., & Inskipp, T. (2011). Birds of
the Indian subcontinent (Helm Field Guides).
Hedrick, B. P., Cordero, S. A., Zanno, L. E., & Noto, C.
(2019). Quantifying shape and ecology in avian pedal
claws: The relationship between the bony core and
keratinous sheath. Ecology and Evolution, 9(14), 8292–
8304. https://doi.org/10.1002/ece3.5507
Hertel, F. (1995). Ecomorphological indicators of feeding
behavior in recent and fossil raptors. Auk, 112(4), 890–
903.
Kerschbaumer, M., & Pfingstl, T. (2024). Multiple factors
influence claw characteristics in mites. Scientific Reports.
Livezey, B. C. (1990). Systematics and morphology of
grebes. Ornithological Monographs.
Martin, E. M., & Sherratt, E. (2023). Grasping hold of
functional trade-offs using the diversity of foot forms in
Australian birds. Evolutionary Ecology.
https://doi.org/10.1007/s10682-023-10261-5
Orkney, A., et al. (2025). Integration of forelimb and
hindlimb morphology in vertebrate evolution. Nature
Ecology & Evolution.
Picasso, M. B. J., et al. (2025). Hindlimb bone proportions
and prey preferences in owls. Zoological Journal of the
Linnean Society.
Pintore, R., et al. (2023). Foot adaptation to climbing in
ovenbirds and woodcreepers (Furnariida). Journal of
Anatomy, 243(4), 567–578.
Prum, R. O. (1990). Phylogenetic analysis of the evolution
of display behavior in the Neotropical manakins (Aves:
Pipridae). Ethology.
Rasmussen, P. C., & Anderton, J. C. (2012). Birds of South
Asia: The Ripley guide (2nd ed.). Lynx Edicions /
Smithsonian Institution.
Siri, S., Ponpituk, Y., Safoowong, M., Nuipakdee, W.,
Marod, D., & Duengkae, P. (2020). Comparing
morphological traits of legs of understory birds inhabiting
Gopal Anapana et al. Int. J. Zool. Appl. Biosci., 10(5), 89-96, 2025
www.ijzab.com 96
forest areas with closed canopies and forest gaps.
Biodiversitas: Journal of Biological Diversity, 21(3),
1041–1048. http://dx.doi.org/10.13057/biodiv/d210326
Sustaita, D., et al. (2013). Getting a grip on tetrapod
grasping: Form, function, and evolution. Biological
Reviews, 88(2), 380–405.
https://doi.org/10.1111/brv.12010
Thomson, T. J., & Motani, R. (2023). Morphological
relationships between vertebrate claw unguals and
sheaths and the functional morphology of these
structures. Journal of Morphology.
https://doi.org/10.1002/jmor.21537
Tinius, A., & Russell, A. P. (2017). Points on the curve: An
analysis of methods for assessing the shape of vertebrate
claws. Journal of Morphology, 278(1), 123–137.
https://doi.org/10.1002/jmor.20625
Tyler, J. (2023). Phylogenetic diversity and morphological
disparity in seabirds (Doctoral dissertation). University of
Bath.
Ziswiler, V. (1965). Der Fuss der Vögel in seiner
funktionellen und ökologischen Bedeutung.
www.ijzab.com 96
forest areas with closed canopies and forest gaps.
Biodiversitas: Journal of Biological Diversity, 21(3),
1041–1048. http://dx.doi.org/10.13057/biodiv/d210326
Sustaita, D., et al. (2013). Getting a grip on tetrapod
grasping: Form, function, and evolution. Biological
Reviews, 88(2), 380–405.
https://doi.org/10.1111/brv.12010
Thomson, T. J., & Motani, R. (2023). Morphological
relationships between vertebrate claw unguals and
sheaths and the functional morphology of these
structures. Journal of Morphology.
https://doi.org/10.1002/jmor.21537
Tinius, A., & Russell, A. P. (2017). Points on the curve: An
analysis of methods for assessing the shape of vertebrate
claws. Journal of Morphology, 278(1), 123–137.
https://doi.org/10.1002/jmor.20625
Tyler, J. (2023). Phylogenetic diversity and morphological
disparity in seabirds (Doctoral dissertation). University of
Bath.
Ziswiler, V. (1965). Der Fuss der Vögel in seiner
funktionellen und ökologischen Bedeutung.