Over the past few years, the Migration Research Foundation has been compiling an online photo library of North American birds, based largely on the banding program at McGill Bird Observatory.  The intent is to provide a visual reference that can be used as a companion to existing text references, such as the "Identification Guide to North American Birds, Part I" by Peter Pyle (Slate Creek Press, 1997) and various other field guides.

In Central America, however, even text references providing details on the molt and ageing of most birds are relatively limited. For Costa Rica there are at least two very good field guides, but neither provides the specifics required to reliably assess age (and in some cases sex) of most species in the hand. At least to some extent, this likely reflects a lack of knowledge about the molting patterns of many resident species.

The Calgary Bird Banding Society has since 2002 been banding resident and migrant birds at a site on the Osa Peninsula on Costa Rica's Pacific Coast. The program has been very successful at banding a large proportion of the resident birds, and documenting their longevity through year-to-year recaptures, including several birds from the first year that have returned annually through 2008. This high rate of recapture also provides an opportunity to compare the appearance of birds from one year to another - in other words, a sample of birds for which at least an age difference is known, and sometimes even an absolute age.

Photos on this website are copyright of Marcel Gahbauer and the Migration Research Foundation, but are presented here with the permission of the Calgary Bird Banding Society; while we welcome anyone to forward this website to others, the photos may not be reproduced or otherwise redistributed without express written permission in advance. E-mail us at with requests.

At this time, we only have photos from the 2008 season, and therefore for most species our interpretation of molt patterns is limited to our knowledge of the approximate age of recaptured birds.  Even this shows us some patterns quite different from those typically seen in North American birds, but we hope in time to add additional photos that will provide more extensive opportunities for comparison.

Some of the comments regarding ageing and sexing are speculative, based on limited data at this point.  Anyone with experience studying any of these species is encouraged to support or challenge any of the statements made.  The intent of this website is to provide a focal point for identifying and discussing characteristics useful for reliable advanced identification of Costa Rican birds, and we hope to add to it over time as more photos and data become available.

Minimal discussion is focused on separating similar species, as this challenge is already dealt with well by published field guides; rather, we concentrate on how to distinguish birds by age and sex within each species.  The text in the photo library assumes a level of familiarity with terminology used by banders with respect to moult and ageing.  We have started to compile an introduction on some of the frequently used terms and techniques, and welcome any suggestions for additions to it.


1) The Migration Research Foundation is pleased to make this resource available free of charge.  However, it represents a substantial investment of both time and funds, so we ask that if you find the Photo Library useful, please consider making a donation to help us maintain and continue expanding it.  The Migration Research Foundation is a registered charitable organization in both Canada and the United States, and can issue income tax receipts to donors.  Click on the button below to make a donation online through a secure site, or here for information on how to contribute by cheque.

2) All photos and text in the Photo Library are copyright of the Migration Research Foundation and may not be reproduced in any manner without prior written consent through contacting us by e-mail

3) We welcome all users to forward this site to friends, or place links to it on your own website, but we ask that you link only to this welcome page, so that all new visitors will have the benefit of the background information above before exploring the species accounts.

Click here to enter the Costa Rican Bird Photo Library

2002- The Migration Research Foundation Inc.