Bird Toe Arrangements

NOTE: Numbering of toes in a “typical” bird

Toe #1 = Hallux (usually rear-facing)

Toe #2 = innermost forward toe

Toe #3 = middle toe

Toe #4 = outermost toe (usually forward-facing)

- Three toes forward, one (hallux) behind
- For perching on branches, etc.
- Common in Order Passeriformes (songbirds), as well as most raptors (hawks, eagles, falcons, etc.), and Order Columbiformes (doves, pigeons)

Bald Eagle perching, showing anisodactyl toe arrangement

Pete Markham from Loretto, USA [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

Black-capped Chickadee perching, showing anisodactyl toe arrangement

Chris [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

- Two toes forward, two behind (2^nd & 3^rd toes in front; hallux & 4^th toe point back)
- Characteristic of Order Piciformes (woodpeckers), as well as some owls, Osprey, parrots (Order Psittaciformes) and cuckoos (Order Cuculiformes)
- In woodpeckers, this arrangement helps in grasping onto vertical surfaces, like tree trunks
- In general, it helps in grasping and moving around on branches, and in grabbing prey

Pileated Woodpecker foot illustration

Chapman, Frank M.; Reed, Chester A. [Public domain], via Wikimedia Commons

Red-bellied Woodpecker modelling his toe arrangement.

Manjithkaini [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], from Wikimedia Commons

- Two toes (middle and outermost) are joined for part of their length and share a broad sole
- Probably an adaptation for excavation of nesting burrow
- Characteristic of Order Coraciiformes (kingfishers, rollers, hornbills, & allies)

Sacred Kingfisher foot

Photo: PookieFugglestein [CC0], from Wikimedia Commons

Sacred Kingfisher

Photo: fir0002 | flagstaffotos.com.au [GFDL 1.2 (http://www.gnu.org/licenses/old-licenses/fdl-1.2.html)], from Wikimedia Commons

- All four toes can point forward (bird can move the hallux and 4^th toes so they point either forward or backward)
- Characteristic of Family Apodidae (swifts)
- Arrangement helps in using toes as hooks for clinging to walls of caves, chimneys, etc.

Chimney Swift clinging to a wall

Photo: Internet Archive Book Images [No restrictions], via Wikimedia Commons

- YOU DO NOT NEED TO KNOW THIS ONE FOR BIOL 225/RENR 401B; it is included here for completeness
- Like zygodactyl (two forward, two behind) but in this case the 3^rd and 4^th toes are in front, and hallux and 2^nd toe are behind
- ONLY found in Order Trogoniformes (trogons)

Red-headed Trogon

Photo: JJ Harrison (jjharrison89@facebook.com) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons

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