Date: 12/30/18 9:03 am From: David Irons <LLSDIRONS...> Subject: [obol] Re: Winter Barn Swallow in Central Oregon
In general, reports of out-of-season birds tend to spike during CBC season, with many continuing to be seen through the remainder of season. Indeed Tree Swallows have long been reported on Oregon CBCs dating back to my earliest days as an Oregon birder, but not so with Barn Swallows. Further Tree Swallows regularly winter farther north and much closer to Oregon than Barn Swallows. Their historical patterns of winter occurrence are not similar.
The appearances of mid-winter Barn Swallows has often been now you see them, now you don’t. They often show up at places that get regular coverage year-round, but do not seem to remain through the season like other semi-hardies found during CBCs. During my 12-year tenure as a regional co-editor for the North American Birds journal my colleagues and I diligently tracked reports of mid-winter Barn Swallows. I can’t recall instances—though there may have been a few—that involved overwintering birds. Most reports involved birds that showed briefly and then were gone. Their inexplicable pattern or lack thereof was unique enough that we regularly commented on it in depth. There was no such discussion of the well-established and regular pattern of Tree Swallows being present in the region (IR and WA) during mid-winter. There is no body of evidence or sightings that suggests Barn Swallows are generally around all winter and only being noticed during the CBC season.
There were Tree Swallows on the Sauvie CBC about 1973. I recall Cliff Swallows reported at Ridgefield NWR the day of the Coquille CBC, about 6 years ago. Then there is the Rough-wing in Clackamas County that showed up in Desember this year a few days off from an appearance at the same spot last Dec.. it was joined by a Violet-green this year. On the Coquille CBC 1/1/17 I think half the teams reported Barn Swallow. In the Norway and Coquille sector three or more birds were involved. The day was marked by regular, small,violent cold fronts, the ground turning white with hail, then an hour of sun , or almost. Don't these cold fronts come at the back of the same cyclone bringing the warm front days earlier?
As Wayne points out, swallow reports spike on CBCs. Observer effort goes up by an order of magnitude, many spots receive a unique annual visit. Then we retreat to comfort
"The now annual appearance–followed typically by an almost immediate disappearance–of Dec–Jan Barn Swallows in the Pacific Northwest remains a mystery that is not easily explained. "
I think it is important to avoid tunnel vision here. Barn Swallows are swallows. They are ecologically a bit different from our other swallows, perhaps, but surely are ecologically more like their fellow swallow species than like any of the other passerines whose ranges or seasonal distributions have changed in recent years.
In 1977, when I left Oregon to move to Florida I did not know of ANY record of ANY swallows in the Pacific Northwest. By the time I moved back to Oregon in 1998 there had been multiple Dec.-Jan records of both Barn and Tree Swallows. Since then we have had records of most (all?) of our other swallows except Purple Martins.
I have difficulty buying the idea that the Barn Swallow occurrences are a special case, with different drivers than the Tree, Violet-green, Cliff, Rough-winged, and Bank swallow witer occurrences.
I also question the reality of the elipsed (?) assertion, "–followed typically by an almost immediate disappearance–." I think birder effort has a lot to do with this impression. Many of the winter swallow records originate on CBCs or CBC scouting excursions. i personally have seen Barn Swallows in Lincoln County twice in mid-January in the past 20 years, and I doubt that either of those sightings is easily extracted from the public record. One was on a winter raptor survey, so there might be a handwritten note on the bottom of a data sheet in Jeff Fleischer's file cabinet (and since I was just an assisting birder and not the person assigned the route, it likely would not be filed under my name. I likely mentioned the other in a post to OBOL, but likely without Barn Swallow mentioned in the post.
In addition, as the beginning of February approaches, Barn (and other) Swallow sightings tend to be thought of as early arrivals, so the possibility of winter residency tends to be discounted.
The now annual appearance–followed typically by an almost immediate disappearance–of Dec–Jan Barn Swallows in the Pacific Northwest remains a mystery that is not easily explained. Arrivals and departures don't appear to be tied to particular weather patterns. When they disappear are these birds continuing north to an ultimate demise (presumably) or are they retreating south? Perhaps they are birds that lingered farther north and are really late southbound stragglers. It has even been postulated that these birds originate from Southern Hemisphere breeding populations and that they are long way the wrong way austral migrants (a la Fork-tailed Flycatcher) that migrate north when they should be heading south to breeding areas.
Climate change could certainly be a factor, but based on the relatively recent and sudden onset of this seasonal anomaly, it is hard to buy into a direct cause-effect relationship. Prior to the early 2000s when the mid-winter Barn Swallow phenomenon first occurred, Barn Swallows were not showing up at all regularly in the PNW during winter. They were also not showing up regularly in Northern California, which might have been precursor to the pattern we've seen of late. If there was a direct connection to long-term climate change I would expect that this distributional change would have come on more gradually like the range expansions of Red-shouldered Hawk, Anna's Hummingbird, Black Phoebe, California Scrub-Jay and Lesser Goldfinch. All of these species have been incrementally expanding their ranges northward into Oregon and more recently Washington dating back to at the 1970's and even earlier in the case of the Scrub-Jay.
Reverse migrations are well-documented in many species, most notably Tropical Kingbirds along the West Coast of North America. Tropical Kingbirds (at least a portion of the population) seems to be 'hard-wired' to migrate north instead of south following the breeding season. It may be that we are seeing a similar mechanism expressed in a small portion of the Barn Swallow population. It would be interesting to capture some of these birds and take some feather and DNA samples to see which population they are originating from, as that seems likely to reveal clues that might help unravel this mystery.
There has been strong air movement from south to north the past little while, which has brought various swallow species to Oregon regularly during CBC season over the many years. Climate change is always happening. As for anthropogenic climate change being the reason behind anything and everything...such unimaginative post hoc propter hoc does a great disservice to science in general. The Eugene CBC recorded a Turkey Vulture once in the 50s.
On Dec 29, 2018 8:53 PM, <clearwater...><mailto:<clearwater...>> wrote:
Hi Craig & All,
A few years back we had a Barn Swallow flying around just as volunteers were coming back in for the countdown at the Thomas Condon Visitor Center in the John Day Fossil Bed National Monument, for the Antone CBC. Recorded for the count.
Definitely a good CBC sighting but not unprecedented. Climate change is happening!
[obol] Winter Barn Swallow in Central Oregon
* From: Craig Miller <gismiller@xxxxxxxxx>
* To: cobol <cobol@xxxxxxxxxxxxxxxxxxxxx>, OBOL Birders Online <obol@xxxxxxxxxxxxx>
* Date: Sat, 29 Dec 2018 20:38:40 -0800
While birding at the Crooked River Wetlands, Marilyn and I observed a BARN
SWALLOW flying along the Crooked River. I am not aware of any other swallow
records in Central Oregon during either December or January.