Winter Finches

(N. B.: after 11 months of blogging about my big year, I thought I would attempt to write something at least somewhat educational.) 

My big year recently received a boost from what is shaping up to be a good finch winter. "What exactly is a good finch winter?" you ask. In this instance, "good" is measured from the perspective of a birder, and a winter qualifies as good with the presence of White-winged Crossbills and Common Redpolls. The local abundance of these species varies among years, and some winters none or very few are present. 

Unlike most northern hemisphere songbirds, White-winged Crossbills do not follow the typical north-to-south migration. Instead, they are nomadic, moving in response to the presence of their principal food. Their geographic distribution is closely associated with that of conifers in the genus Picea, and their movements are linked to patterns of conifer use.

A probability of observation (PObs) map for White-winged Crossbill, taken from the BC Breeding Bird Atlas (http://www.birdatlas.bc.ca). The PObs maps are created by incorporating topographic variables into models to make predictions about the likelihood of detecting a species in all areas of the province, within a fixed amount of time (20 hours). Granted this map is based on data collected by atlases during the breeding season, I would still like to point out the 0% probability of observation in Metro Vancouver (click map to enlarge).  

In late June and July, the cones of most conifers are developing and seed inside cones of tamarack and white spruce are among the most accessible. In May, White-winged Crossbills are often on the move as birds search for developing white spruce cone crops sufficiently large to support breeding. White spruce cones shed most of their seed between mid-September and early November. Crossbills generally remain in the area as long as seed abundance is high and leave once it declines, switching then to black spruce. Black spruce cones open later in the year than white spruce and their seeds often remain inside their cones through to the following summer. In late spring, White-winged Crossbills typically migrate from areas of black spruce to areas with developing white spruce cone crops regardless of black spruce seed availability. When the spruce cone crop is poor, crossbills can irrupt into regions south of their usual range in search of good cone crops.

Distribution of three spruce (Picea) species in British Columbia, taken from the Tree Species Compendium (https://www.for.gov.bc.ca/hfp/silviculture/compendium/index.htm). Top to bottom: Engelmann spruce, black spruce and white spruce. Notice any similarities to the White-winged Crossbill probability of observation map?

Though perhaps not quite a full scale irruption, some White-winged Crossbills have turned up on Mount Seymour this winter and were a welcome addition to my year list.

#253. White-winged Crossbill. 20 Nov 2015. Mount Seymour.

While crossbills are nomadic, Common Redpolls are considered ‘irruptive’, meaning they exhibit regular seasonal movements, the extent of which varies between years. One suggested cause behind their irruptive movements is their dependence on birch and alder seeds. Seed shortages may cause redpolls to travel farther from their breeding range in winter, stopping when they encounter sufficient food rather than a pre-programmed destination.

#254. Common Redpoll. 21 Nov 2015. Sea Island.

Redpolls have been reported widely this November, but seemingly from everywhere where I was not. It took some time before finally finding some of my own on Sea Island.

Count Update: 254 + 2 on Nov 21.

Back to Back Birds at Pt. Bob

After a bit of a lull, I got 252 + 1 and 252 + 2 both at Pt. Roberts.

You may recall from an earlier post that there are two versions of the Vancouver checklist area, one which includes the small peninsula of Pt. Roberts in Washington, and one that doesn't. Thus far I have made a (completely unnecessary) effort to keep both versions identical for numerical simplicity. However, after seeing a Rock Wren (#252 + 1) at Pt. Roberts on November 1st, my lists have once again diverged and will likely stay this way given the local rarity of this species. 

The main significance of this Rock Wren is that it was #250 for MEHA, the fourth person to join the 2015 250 Club. And so I would like to extend a big congratulations to someone who has greatly facilitated the rapid exchange of rare bird alerts and contributed immensely to everyone's Big Years. 

#252 + 1. Rock Wren. November 1, 2015. Pt. Roberts, WA.

After seeing several Ancient Murrelets (#252 + 2) at Pt. Roberts on November 15, I still felt compelled to make an effort to see them in the eBird Metro Vancouver county. My efforts since have included a sea watch from the end of the Iona south jetty, which produced only Marbled Murrelets, and a walk-on sailing on the Tsawassen-Duke Pt. ferry, which produced Ancient Murrelets only on the Vancouver Island side of the sailing, as determined by plugging GPS coordinates into eBird. It has been a great deal of (completely unnecessary) effort for a semi-year bird. Life would be much easier if birders ignored the international border across Pt. Roberts just the same as these murrelets do. 

 Count update: 252 + 2 on Nov 15.

October Briefly

October passed quickly with limited gains. The waning daylight impeded my birding before and after work, a whirlwind of rare birds outside Vancouver took my focus off the task at hand and field work took me out of town for a few days. Consequently, the effort I devoted to my Big Year was limited, as reflected by my piddly submission of only 13 eBird checklists from 9 days. However, there were two notable additions to the list.

A Clark's Grebe, which as rare birds always do, showed up while I was out of town. Fortunately it remained in the area for a couple weeks, swimming back and forth between the White Rock pier and offshore waters of Semiahmoo Bay. On some days it would thrill observers with close up views, while on others it was likely unresolvable among the distant flotilla of Western Grebes. I caught him somewhere in between.

#251 - Clark's Grebe - 9 October 2015 - White Rock Pier. The Clark's Grebe is on the right, with a Western Grebe on the left. With some stretch of imagination you may be able to see paler flanks and a narrower black stripe down the hind neck of the Clark's. And if you stare long enough, you may even be able to convince yourself that it has white lores. 

On October 12th a Tropical Kingbird was photographed along the Richmond West Dyke. Although this species has become of increasingly regular occurrence in recent years, it still remains an extremely rare bird for the area. According to the eFauna Checklist of Rare Birds of the Vancouver Area, there were only 3 records prior to 2008. This bird represents at least the 5th record since then, of which I've now gone 5/5.

#252 - Tropical Kingbird - 13 October 2015 -  Richmond West Dyke at Steveston Hwy.

But to balance these successes there was also great sorrow, the likes of which is known by few: on October 16 I missed a Blue-gray Gnatcatcher found by KELO at Boundary Bay. It was successfully twitched by several first responders¹, however, being the responsible employee that I am, I remained at the office until the afternoon by which point the gnatcatcher was never to be seen again.²

Two other birders joined the "2015 250 Club" in October and deserve special commendation: MITO on Oct 4 and ROLY on Oct 27. Well done both of you!

Count update: 252 as of Oct 31.

Footnotes:
¹Apparently I also missed quite a celebratory dance which I would have liked to see almost as much as the gnatcatcher.
²Despite blogging in anonymity, my blog has been discovered by some co-workers leading to suspicions about my priorities. Surely this sacrifice will alleviate all such concerns.