Detailed Guide to Nestling Development Available

The U.S. Fish and Wildlife Service has posted an electronic copy of recent issued publication about bird nestlings. A Guide to Nestling Development and Aging in Altricial Passerines is well illustrated – with pictures and diagrams - with numerous details on the different variables essential to accurately age nestlings, how to measure the size of birds in the nest, as well as applicable terminology.

The objectives for the publication are: 1) "to report and promote research on species specific patterns of altricial passerine nestling development and aging," and 2) "to achieve better estimates of nestling ages."

PRBO biologists collaborated with the Fish and Wildlife Service to prepare the guide, issued as Biological Technical Publication, BTP-R6008-2007.

"The guide is more geared towards field biologists with nest survival studies or ornithologists interested in nestling growth," said lead author, Dennis Jongsomjit, of the Point Reyes Bird Observatory. "Time in the nest is a very important part of a birds life, not only while it's a nestling, but even as an adult and for the population as a whole as well. By studying nestlings and the environment they grow up in we can start to make connections with the type of habitat and conditions needed to successfully fledge young that will go on to breed successfully.

Yellow-breasted chat (Icteria virens). Detail of photograph by Chris McCreedy/PRBO, as included in the publication.

"However, there is still relatively little known about growth and aging for many species and what info there is is widely scattered. We thought there was a need to summarize the information, provide a methodological template for future studies, provide guidelines for aging, and at the same time bring in new data for a set of species to serve as an example. I think field biologists will find the daily descriptions and photographs very useful (like a field guide) and something they can adapt to whatever species they are studying.

"Getting detailed daily growth data is a very time intensive process. This automatically limited the number of participants that could get fully involved. We definitely appreciated the commitment and time put in by our contributors.

"We wanted a diverse set of species, but we knew that time commitments for this project would be limiting, thus we were really looking for any researchers out there that would be willing to help with their study species. Luckily, we did manage to get a diverse group of species. Internally, our focus was on species we have been studying (nest monitoring) for many years. Getting development data for them would improve our data set in the years to come."

Detailed nestling development accounts are provided for these species:

• Dusky Flycatcher (Empidonax oberholseri)
• Carolina Wren (Thryothorus ludovicianus ludovicianus)
• Wrentit (Chamea fasciata rufula)
• Sprague’s Pipit (Anthus spragueii)
• Song Sparrow (Melospiza melodia gouldii)
• Chestnut-collared Longspur (Calcarius ornatus)
• American Goldfinch (Cardeulis tristis)

Each account includes a summary of nesting characteristics, and a day-by-day picture – of varying quality - of the nestling, being available in most cases. Also given are feather tract development, and morphometric data, and a general description.

The publication was issued in October 2007 and is one of many biological publications available from the online library maintained by the Fish and Wildlife Service.