The Putah Creek Riparian Reserve, owned and managed by UC Davis, is a well-known birding spot. The publicly accessible Yolo portion is on the north bank of the creek, mainly between County Road 98 (called Pedrick Road in Solano County) and Brooks Road.
The Reserve was established in 1983. We have a good picture of changes in bird abundance since then, because of the data in eBird. Perhaps due to its popularity, the Reserve has two eBird hotspots, “Putah Creek–Levee Road” and “Putah Creek–Pedrick Road”, which appear to cover the same ground. Checklists for Levee Road start with 1987; those for Pedrick Road begin with 2004.
For analysis, I divided sightings into three roughly equal periods, referred to as early, middle, and recent. The conspicuous trends, and some possible explanations, appear below.
Turkey vulture was absent in winter in the early and middle periods, but now occurs all year. I attribute this to the recent dwindling of winter fog. Wild turkey was absent early on, then appeared in spring and fall, and recently has occurred year-round. This likely reflects its gradual establishment following an intentional introduction into our region. Collared dove appeared only recently, matching the timing of its expansion elsewhere in the county.
Cooper’s hawk was not seen in the breeding season till recently. While the species has become a fairly common breeder in our cities, presumable because more trees have grown tall enough for nesting, this explanation doesn’t seem right for the Reserve. It’s a puzzle.
Acorn woodpecker, a species regarded as rather sedentary, has been on-again, off-again. It was present in fall and winter in the early years, then absent altogether in the middle period, and is now seen all year. Likewise, northern flicker was present all year at first and recently, but only in winter in the middle years. Did West Nile fever play an unrecognized role in the middle period?
Ash-throated flycatcher, tree swallow, and western bluebird share a pattern of absence (bluebird) or near absence in the breeding season until recently, when they have become common. This change surely owes to the recent provision of nest boxes for their use.
Two other hole-nesting birds, white-breasted nuthatch and house wren, were missing in the breeding season until recently, and are now common all year. They are not big users of nest boxes at the Reserve, but perhaps the many boxes eased competition for natural nest cavities.
Oak titmouse was absent early on, appeared only in April and late summer in the middle years, and has been sporadic all year recently. This inconsistency is unexpected in a species thought to be highly sedentary. Furthermore, in the last two years I have not found titmice at the Reserve, but some other birders have. Charitable explanations of this difference are welcome.
Hooded oriole was absent in the early years, present only in late summer in the middle period, and now occurs through spring and summer. This matches its population increase in the wider area in the recent period.
Those are the highlights, made possible by the efforts of local birders using eBird. Note that the January meeting of Yolo Audubon will examine the capabilities of eBird more closely.
Michael Perrone, Conservation Chair, YAS