San Diego Natural History Museum--Your Nature Connection[San Diego County Bird Atlas Project]

The quarterly newsletter for Bird Atlas volunteers
Fall 1998

In this Issue
Confirmation Cues

Notable Observations

Reports from the Field
Birds' Response to Changing Habitat on the Floor of the Borrego Valley
American Bitterns Nesting at Camp Pendleton
The Heron and Egret Rookeries of San Elijo

Focus On...
The Black-throated and Sage Sparrows

News and Updates
Watch Out for Those Killer Bees
Blockbuster Weekends
Our Fall Wingding

Confirmation Cues

As we all gain experience learning the cues confirming the breeding of various birds with diverse behavior and lifestyles, let's use the medium of Wrenderings to share them with other bird atlas participants. My conversations with several participants, especially Ed Hall, led to the following list of tips.

First thing to focus on when you see a bird: the bill. Is it carrying nest material or a bill full of crushed insects? For the great majority of species, carrying nest material or food for young is behavior confirming breeding. Watch the bird for a minute or two to see whether it's carrying the prey back to a perch to be killed and eaten by the adult itself. If the bird carries the prey any distance or is accumulating insects in its bill, it's certain the food is destined for young. Only in the case of the few habitual food-cachers, the jays and Acorn Woodpecker, does carrying food a distance not imply feeding young, and even those species cache nuts, fruit, and acorns, not insects.

Spread your effort in the field through the whole spring and summer. Though the threshold criteria are designed to get you out into the field at times when the greatest number of species will have fledglings in tow (June on the coastal slope, May in the Anza-borrego Desert), some species are engaging in their most conspicuous behavior earlier or later.

Find a likely spot with a few birds flitting around, sit silently for 5 or 10 minutes, and see what pops up—often quite a lot. Hurried hiking and crashing through brush will generate almost nothing. Once you spot a bird, stay with it for a moment to see what it does.

Seemingly odd behavior may be a clue to something interesting. For example, swallows don't normally land on the ground except to pick up next material, grass for nest-lining in the case of the Rough-winged and Violet-green as well as mud for the Cliff.

Listen for unfamiliar calls—especially if they sound like those of baby birds—and track them down. Even if you don't find the young, the adults usually give themselves away with alarm calls or distraction behavior. The calls of fledglings are just as distinctive to species as those of adults and can be learned with practice.

Spread your effort through the day. Ed Hall suggests that in the first hour or two after dawn the adults are too preoccupied with feeding themselves and advertising their territories to engage in much breeding-related behavior. Later in the day may be the best time to see things like nest-building and feeding of young. Certainly many of my confirmation came in the late morning. Does anyone else have observations that reflect on this question?

Don't interpret the behavior codes too narrowly. For example, for "NB" it is not necessary to see the bird add the twig to the next; just seeing it carrying the twig is sufficient. For "FY" it is not necessary to see the adult stuff the insect down the young bird's throat; just seeing it carrying the insect, as described above, is sufficient. And especially critical case is the distinction between fledgling (FL) and juvenile (JV). Even if the young are flying well, if they are following their parents in an obvious family group, count them as fledglings. If they are making begging calls characteristic of fledglings, count them as fledglings.If they still have noticeably fleshy corners of the mouth (usually colored yellow or pinkish), count them as fledglings. If they re independent of the adults or part of a flock larger than a single family count them a juveniles.

I welcome your tips for confirming breeding for inclusion in future Wrenderings and hope to schedule more programs and training sessions related to the atlas around the county before the beginning of the next breeding season.

 -- Philip Unitt

Wrenderings Archive | Bird Atlas Introduction