About Aging and Sexing Birds

Pyle, 1997 and 2008 - The Standard Age/Sex References

The Identification Guide to North American Birds: Part 1 and Part 2 by Peter Pyle are landmark volumes, and with few exceptions are to be considered the final word on what the BBL/BBO will accept from banders to be incorporated into the main database. The acceptable age and sex quality checks in Bandit are based on these guides.

These guides are intended to replace the existing keys in the North American Bird Banding Manual, V. 2. All use of other, older information (e.g. Wood's Manual) should be discontinued. Banders should purchase and use the new Pyle guides as the primary reference to aging and sexing bird species in North America. Banders may continue to use the North American Bird Banding Manual V. 2 during the transition period, except for Summer Tanager and Common Yellowthroat. The Pyle guides represent the opportunity for banders to have a common reference, and we are sure that the benefits this represents will make all the effort needed to learn to use this book worthwhile. Thanks to Peter Pyle for working closely with both the US and Canadian offices to ensure acceptance of this new guide as the North American standard reference for all species covered.

The BBL will not expect banders to micro-age every bird, this is why we have the codes AHY, ASY, etc. It is very important to not guess at ages and sexes. AHY is not incorrect when SY and ASY are allowed; it is not as informative but it is not incorrect. Banders should do their best to learn to use these guides but should not feel pressured to identify every individual bird to a precise micro-age.

We expect that there will be some transition time for banders to learn to use these guides., Please keep an open mind about them, they are not that difficult to use once you spend some time with them! Read the section Directions for Use carefully, and learn to interpret the bar graphs before using these books in the field. All banders will find that it will take some time to learn to use them correctly, but the effort will be well worthwhile. For those who have never been through a major change in banding techniques like the advent of skulling or the original appearance of the dichotomous keys in Volume 2 of the Banding Manual, please have patience learning to use theseguides, and by all means seek out banders who are using the guides and ask for assistance.

With the large amount of new information present in these guides, it is not unexpected that some characteristics will be found less useful than was thought at the time of publication, and others will be found to be more reliable. These guides represents one uniform starting point for all banders, and banders are asked to contribute to the next edition by publishing information on aging and sexing criteria in the relevant journals or by writing to the author or BBL.

Please note that acceptance of specific age codes is only for those techniques in the book, and does not necessarily indicate acceptance of other techniques. Banders may continue to use peer-reviewed information in the major journals as it is published in addition to the new Pyle. Additions and corrections for the new guide can be sent to the BBL, and will be forwarded to Peter as well. Please contribute!

We regret that we can not supply these books to banders as we have supplied the North American Bird Banding Manual in the past. We hope that the additional information in the new Pyle will offset the added expense to banders.

This book can not be ordered from the BBL. To order, contact Slate Creek Press at P.O. Box 219, Bolinas CA 94924 or click here to go to Point Reyes' Bird Observatory ordering information page.

Go to IBP's webpage for errata.

Learning to see molt limits and using Pyle

A new guide from Slate Creek Press is available to help banders learn to see molt limits and interpret them using Pyle (1997). The guide is called Ageing North American Landbirds By Molt Limits And Plumage Criteria: A Photographic Companion to the Identification Guide to North American Birds, Part 1 and it is written by Dan Froehlich. This guide contains 32 color photographs illustrating molt limits and ageing criteria, and points out juvenile, first-basic, alternate, and adult-basic feathers among wing coverts, primaries, and secondaries. For more information see http://www.birdpop.org/danflyer.htm.

Sam Carney's Wing Key

For waterfowl, another very useful guide is Sam Carney's photographic guide to aging and sexing ducks by wing plumage. This guide includes techniques for the identification of selected species as well as information on aging and sexing ducks. The wing keys were developed for the Waterfowl Parts Collection Survey. Species, Age and Sex Identification of Ducks Using Wing Plumage.

When is an HY bird not an HY?

HY indicates that a bird was hatched in the calendar year when it was banded. But HY is not the only code for a bird-of-the-year. We ask banders to distinguish unfledged chicks in nests or any bird too young to be capable of sustained flight (called a pullus in much of the world). The correct code for such birds is L (numeric code 4) for local. This allows the separation of those birds that could have traveled to the banding site from those that were certainly hatched where they were banded.  This code should only be used during the breeding season, and is not intended to be used because you know or suspect that the bird was hatched locally.

Age Unknown from January 1 to the Nesting Season

It is not appropriate to use age U from January 1 until the species typically fledges young each year. By definition these birds are AHY. If you cannot micro-age a bird (SY or ASY), the correct default age at this season is AHY. On January 1, the bird cannot have hatched in that calendar year (now one day old), so it must be an After Hatch Year (AHY) and cannot be an Unknown. If the bird in your hand cannot have hatched and fledged in the current calendar year (January 1 until the day you caught it) it cannot be an Unknown/U but must be an AHY if no more precise age can be determined.

Using Brood Patches to Sex Birds

For many species, both males and females can develop brood patches, and for most of these, there is a marked difference in size and extent between males and females. As an example, Black-billed and Yellow-billed Cuckoos develop brood patches, but the brood patches are identical in males and females. Therefore, neither may be sexed by brood patch. When sexing a species by brood patch, make sure that both females and males do not develop one.

Brood Patch or Cloacal Protuberance and Age

True brood patches (BPs) and Cloacal Protuberances (CPs) are only found in birds in reproductive condition. With very few exceptions, BPs and CPs are not found in HYs. A bird with a BP or CP must be an AHY if a more precise age cannot be determined. It is important to emphasize that the BP must be a true BP and not the bare unfeathered belly of a recently fledged juvenile.