The Santa Cruz County Breeding Bird Atlas II is moving along. We are now well through the third year of field work out of five years anticipated. This puts the project over the half way mark! Good progress is being made in areas of Santa Cruz County where there was little atlasing in previous years and many new and rare observations are improving the knowledge of our breeding birds.
The atlasing season began in March and since then atlasers have spent over 1,100 hours in the field-wow! The project is truly powered by the many atlasers that are participating. There have been many highlights through early June, some of which are below.
Extensive atlasing in the Pajaro Hills east of Watsonville have found some rare species are breeding more widely than was previously known. Numerous pairs of Blue Grosbeaks and Western Kingbirds, as well as Lark Sparrow are among those whose breeding status and distribution is changing as a result of atlasing in areas rarely visited. Other nice finds so far include a Hermit Warbler nest at Big Basin State Park and an American Bittern nest at Pinto Lake. Very few nests of these species have previously been found in the county.
For some species such as Western Bluebird, atlasers are documenting the continued recovery of the local breeding population. Atlasers are revealing just how widespread this species really is now as new breeding locations continue to be discovered, the latest being at Arana Gulch where they immediately took to the new nest boxes placed there earlier in spring. Other species such as the Tricolored Blackbird are still on the decline as apparent from atlasers noting most recently active colonies are vacant.
In addition to longer term population changes, atlasers are documenting annual fluctuations for some breeding species such as colonial waterbirds. Pelagic Cormorants are doing poorly this year compared to 2018; there are about 65% fewer active nests than last year, and half the colonies in the county have been abandoned. While not as dramatic of a drop, there are also about 25% fewer Great Blue Heron nests than last year.
We are also learning more about the phenology of many species-when the nest building, nesting, and fledgling periods are in the year. The many observations from backyards where breeding activity is frequently and easily observable greatly contribute to understanding the phenology of our breeding species.
There are still about six weeks left of the atlasing season and there is no better time to go look for breeding activity than now. Most species are still breeding and can be seen carrying food and tending to recently fledged young. My thanks to the atlasers for contributing so many observations and the many supporters whose donations keep the project moving forward. I look forward to sharing cumulative results in the atlas annual report and more highlights in the Albatross later this year.