How Do Young Birds Know When To Leave The Nest?

Adult gray-headed junco (Junco hyemalis caniceps) enticing one of its youngsters to leave the nest. Parents hold food away from nest and tempt the young come out to get it. This picture captures a young bird that was just fed outside of the nest.
(Credit: T. E. Martin, doi:
10.1126/sciadv.aar1988)
A young gray-headed junco (Junco hyemalis caniceps) is captured leaving the nest, with its sibling still in the nest in the background, illustrating the under-developed nature of wings when this species leaves the nest.
(Credit: T. E. Martin, doi:
10.1126/sciadv.aar1988)
Cavity-nesting birds, like this mountain chickadee (Poecile gambeli), about to feed its young, have safer nests that allow young to stay in nests longer and develop their wings for improved flight at leaving.
(Credit: T. E. Martin, doi:
10.1126/sciadv.aar1988)
Fig. 6. Wing length and mass with respect to fledgling mortality rates. (A) Mass and wing length as a proportion of adult size in control versus experimentally enclosed nests for gray-headed junco. Control nests fledged at normal age (11 to 12 days), whereas enclosed nests prevented young from leaving for 3 days after fledging naturally to create a delayed fledge age. (B) Photos of typical wings of junco young from control versus experimentally delayed nests on fledging day versus release day, respectively. Β© Daily mortality rate (Β±1 SE) decreased among fledglings with increasing wing length at fledging in juncos. (D) Mortality rate of junco fledglings for the first week after fledging in nests where fledge age was experimentally delayed had substantially lower mortality rate than fledglings from control (normal fledge age) nests and comparable to other species based on wing length. (E) Daily mortality rate of fledglings and nestlings when based on estimates per offspring versus per brood across eight species. The line represents equal fledgling and nestling mortality rates. (F) Nest predation influences evolution of fledging age and growth rates of offspring with consequences for relative development when young fledge, which thereby influences locomotor performance and fledgling mortality. Fledgling mortality, in turn, feeds back to further influence evolution of the age of fledging and traits that affect performance and mortality, but parents and offspring conflict on the optimal fledging age.
(doi:
10.1126/sciadv.aar1988)

Source:

--

--

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
𝐆𝐫𝐫π₯π’πœπ’πžπ§π­π’π¬π­, scientist & writer

𝐆𝐫𝐫π₯π’πœπ’πžπ§π­π’π¬π­, scientist & writer

PhD evolutionary ecology/ornithology. Psittacophile. scicomm Forbes, previously Guardian. always Ravenclaw. discarded scientist & writer, now an angry house elf