Introduction

Phenology is the study of how seasonal environmental changes influence regularly occurring biological phenomena.  When birds breed and how many eggs they lay are the descriptive data essential to the study of avian breeding phenology. The timing of breeding may be affected by geography and elevation over an area as large as the state of Washington, and by yearly variation in weather and other environmental conditions at particular localities.  Average clutch size is known to change through the season in many species, probably most generally because later-fledged young are less competitive, thus forcing parents that raise late broods to increase the quality of fledglings from those broods by investing more in them on a per individual basis.

In the following species accounts we present summaries of the timing of laying and how it is affected by geography and elevation, summaries of clutch size variation and how it changes with season, and a list of the counties from which we have records of breeding for Washington birds.

These data come from three principal sources: the Northwest Nest Record Program, museum egg collections, and field notes.  Since 1955 the University of Washington Burke Museum has maintained a collection of nest record cards contributed by students, professionals and amateurs.  These files now contain over 12,000 cards, principally from Washington but also from Idaho, Oregon, British Columbia, and other areas.

In addition to using the data from cards we have extracted breeding records from field notes from as early as 1889, and from many egg sets collected in Washington and now housed at either the University of Washington Burke Museum (UWBM), the University of Puget Sound (PSM), the Washington State University Connor Museum (WSU), or the Western Foundation of Vertebrate Zoology (WFVZ).  For a few species we have also included data extracted from collected adults, providing that the measurements associated with these specimens provided accurate estimates of first-egg dates or of clutch size.  As collections at the University of Washington and elsewhere become fully computerized, more and more breeding records associated with traditional specimens will become conveniently accessible.

The accounts that follow summarize one or more nesting records for 220 of the 244 species listed as Washington breeders in the Washington State Gap Analysis (Smith, et al. 1997).  We list the species for which we have no records to alert observers to the special need for filing cards for these species.

A cursory examination of the accounts presented here reveals great variability in the numbers of records and their distribution across Washington.  Much of this variability is explained by the ease with which nests may be found and by their accessibility to observers.  The early egg collectors were master nest finders.  Thus, for many species most records come from the late 1800’s and early 1900’s, simply because contemporary observers rarely find their nests.

Certain seasons and areas have been worked intensively by students and professionals.  Between 1975 and 1980 students at the University of Washington filled out nest record cards as part of their course requirements in Ornithology.  These records are noted in the accounts because they are concentrated at the beginning of the breeding season in April and May, before spring quarter ends in early June, and because most come from the greater Seattle area.  Many records come from Grant County because Rohwer and his students recorded numerous nestings in the area of Winchester and Frenchman Hills Wasteways while studying blackbirds there in the 1970’s and 1980’s.  A few professionals have filed cards from their studies, thus we have many cards for Red-winged Blackbirds, Canada Geese, Golden Eagles and Chukars.