They’ve been increasing at a rate of 1.8% per year, strongest in Seattle (3.1%/yr) and weakest in Vancouver (-2.5%/yr, the only count with declining numbers). The five counts, in aggregate, tally between 100 and 750 individuals each year. Growth has been strongest on the Olympia count (4.6%/yr) and weakest on the Bellingham count (1.7%/yr).ĭespite the eBird map, White-crowned Sparrow is a regular overwintering species in the PNW. In each of the last five years, these counts, in aggregate, tallied between 34 and 52 individuals. To put this in perspective, these five CBCs tallied 5 or fewer individuals, summed across all counts, in each of the first five years of this analysis. Lincoln’s Sparrow has been increasing steadily, from near zero, at an overall rate of 3.6% per year. They are increasing the most on the Portland count (3.0%/yr). To illustrate the unpredictable nature of waxwings, they have actually been declining on the Olympia (-2.3%/yr) and Vancouver (-4.1%/yr) counts. That said, it has been above average 8 of the last 9 years. Of the six species I focused on, Cedar Waxwing showed some of the most erratic growth, averaging only 2.5% per year. It has been increasing across all five of the counts, most strongly in Vancouver (4.1% annual growth) and most tepid in Seattle (0.6%). It is most common on the Portland count, which has averaged 26 Hermit Thrushes per count since 2009. Hermit Thrush has been increasing at a rate of 4.2% per year across all the CBCs. The graphs show the birds per party hour across the five CBCs, taking the total number of birds and dividing by the total number of hours across all five counts. Red=summer blue=winter purple=year-round yellow=migration.
The range maps are from eBird’s Abundance Maps. I’ve got more notes on my methodology at the end.Īll have increased since 1975, generally with the uptick beginning in the 1990s. I looked at their numbers and trends on the Portland, Olympia, Seattle, Bellingham, and Vancouver BC CBCs since the 76 th CBC (winter 1975-76). For each of these, the PNW is at the northern limits of their wintering range. They are: Hermit Thrush, Cedar Waxwing, Lincoln’s Sparrow, White-crowned Sparrow, Orange-crowned Warbler, and Yellow-rumped Warbler. This caused me to take a closer look at the data, focusing on Passerines that are rare or uncommon, and at the northern edge of their wintering range. Now in Port Townsend, Washington, we set a local CBC record for Yellow-rumped Warblers last year. Fruit and insects were available to these birds. My bougainvillea and cape honeysuckle, which previously clung to life in winter, were now growing and blooming year-round. We had crossed a threshold we didn’t get freezes anymore. Cassin’s Vireo, Black-throated Gray and Townsend’s Warblers, and Western Tanagers were becoming more expected in winter. As the Putah Creek Christmas Bird Count (CBC) compiler, it was hard not to notice the trends. I’ve previously written about an increase in insectivore bird species in winter associated with a warming climate in the Sacramento Valley. Lehikoinen 2014, Hitch and Leberg 2007, and La Sorte and Thompson 2007).Īnd some have documented poleward range shifts specifically for wintering ranges (Saunders et al 2022, Hampton 2019, Paprocki et al 2017, Prince and Zuckerberg 2016, and Paprocki et al 2014). Many studies have already documented that this is happening (Illán et al. Many papers predict that bird ranges will shift northward with a warming climate (Wu et al 2018, Langham et al 2015).
0 kommentar(er)
