Altricial vs. Precocial Development

• species whose foods require flight and/or experience
• species whose foods are abundant (predation > starvation), and
• species whose nests are relatively less vulnerable to predation.

• species whose foods can be obtained by inexperienced, flightless young,
• species whose foods are scarce (predation < starvation), and
• species whose nests are vulnerable to predation.

Altricial vs. Precocial Development

Advantages and Disadvantages....

Disadvantages of Precocial Development...

• slow growth rate = higher young mortality ( Long time to avoid predators without the benefit of flying)

Benefits of Altricial Development....

Benefits of Precocial Development...

• Slower growth rate = lower food demands
• shorter nestling period (minimizes the vulnerable nestling period)
• chicks are more independent
• less time spent being incubated

• Rapid growth (fed large nutrient-rich food items by parents)
• chicks become independent relatively quick
• minimizes young mortality
• allow the brain to grow well in size
• capable of growing into an ultimately more more developed state

Joanne Sabra & Patrick Hallis

Disadvantages of Altricial Development.....

• Fast growth rate = high food demand
• Extended nestling* period (confined to their nests)
• Parents have to incubate the chicks

*nestling: baby bird in nest. ( too young to leave the nest)

Altricial Development....

• Hatch with eyes closed
• Little or no down*
• Cannot leave the nest
• Fed by parents
• Cannot maintain their own body temperature.

Food Supply...

*Down: layer of fine feathers under the tough exterior feathers

Precocial Development....

What Do They Mean?

Nest Accessibility...

• If food is difficult to obtain, then altricial development is favored
• If food is relatively easy to obtain, precocial development is possible, and in some cases, favored.
• If food is in high supply, then altricial development is favored
• If food supply is low, then precocial development is favored

• Hatch with eyes open
• Covered with down
• Can leave the nest (within two days)*
• Feed themselves
• Can maintain body temperature on their own

*However, they cannot fly yet!

• If nests are inaccessible, then altricial development is favored
• If nests are very accessible, then precocial development is favored

Variables That Influence The Choice of an Optimal Strategy...

http://www.stanford.edu/group/stanfordbirds/text/essays/Precocial_and_Altricial.html

Nature of Young Bird Predation...

"Precocial" and "altricial" are just scientific jargon for the degree of development in birds.

• If nest predation is a less of a limiting factor than predation of freely moving young birds, then altricial development is favored
• If nest predation is more of a limiting factor than predation of freely moving young birds, then precocial development is favored

The End...

http://www.stanford.edu/group/stanfordbirds/text/essays/Precocial_and_Altricial.html

Left: House Sparrow hatchling (altricial- naked, eyes closed, helpless). Right: Ruffed Grouse hatchling (precocial- down, open eyes, mobile, follows parents and is shown food by parents)

Thank you!

Patrick H. & Joanne S.

Works Cited:

• "Precocial versus Altricial Development." Maine Birds RSS. Wordpress MU, 6 Aug. 2009. Web. 27 Nov. 2013.
• "Precocial and Altricial Young." Precocial. Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye, n.d. Web. 27 Nov. 2013.

Chick nestlings

Red-cockaded

Woodpecker nestling

wallpaperswide.com

www.bradybeckphotography.com

Barn owl nestlings

wildatheartowls.org

Kingfisher nestlings

www.arkive.org

Summary of Patterns...

Summary of Patterns cont'd...

Precocial Development

Altricial Development

Precocial Development