My observation is simply that Tree Swallows are dominate over
Violet-greens and displace them from boxes, especially near prime
foraging habitats like wetlands or riparian corridors. This seems quite
noticeable in outer Point Reyes where I've been atlas birding. Holes in
Alder snags along streams are entirely taken by Tree Swallows; holes in
dryer more upland areas often by Violet-green. And in the inter-specific
aggression I've observed, the Tree Swallows win 100% of the time.
In a prior life I put out quite a few boxes in eastern Washington and
north Idaho and VG Swallows seemed happy to take them. Again, well away
from wetlands and wet meadows.
I think it's a dominance thing.
-Rusty Scalf
On 2024-04-24 15:58, Alvaro Jaramillo wrote:
> Dominik
>
> To add to your comments, I don't think that Violet-green Swallows are generally all that keen on nest boxes. They can take them, and in some regions often do, but it is not their preference. They are entirely unlike Tree Swallows in this respect, as Tree Swallows love nest boxes. Here in Half Moon Bay, where Violet-green Swallows commonly nest, they tend to nest in the eaves, holes, nooks, crannies of houses. The few Tree Swallows that nest here are in boxes!
>
> My guess is that out in the wild away from people Violet-greens are more likely to take a rough hole, a crack in a branch, a crevice in an old snag as opposed to a woodpecker hole. On the other hand, flicker and woodpecker holes are the go-to for Tree Swallows.
>
> Alvaro Jaramillo
>
> <alvaro...>
>
> www.alvarosadventures.com [1]
>
> From: <SFBirds...> <SFBirds...> On Behalf Of Dominik Mosur
> Sent: Wednesday, April 24, 2024 2:42 PM
> To: SF Birds <sfbirds...>
> Subject: [SFBirds] recent migrants and breeding notes
>
> migrants continue to pass through the City. In addition I've been monitoring breeding activities; even as some mid-range migrants are just beginning to arrive resident species are producing young for several weeks now. Unfortunately as happens every year, I've noted several breeding efforts disrupted or thwarted by human activity (gardening, weeding, tree trimming) both by private parties and work crews for local land management agencies.
>
> Here's a few sightings I found notable from the past few days (in taxonomic order):
>
> Pied-billed Grebe - 3 first of '24 juveniles observed in the SE corner of Laguna Honda Reservoir, off Clarendon/below the bee hives 4/23
>
> White-throated Swifts - nowadays seem nearly ubiquitous in SF during the breeding season foraging low, and I suspect they are nesting/prospecting for nests much more widely than we may realize. Yesterday (4/23) while in the easternmost end of GoldenGate Park above McLaren Lodge I noted one bird buzzing around the top of St. Mary's medical building on Stanyan.
>
> Rufous/Allen's Hummingbird - a female Selasphorus seen very briefly on Corona Hill 4/24 where there have been no sightings of Allen's this year. Timing suggestive of migrant Rufous
>
> Band-tailed Pigeons - continue to be seen daily in the areas of Mount Sutro/Davidson/Forest Hill neighborhood and almost certainly nesting there again this year as in 2023 and '22.
>
> Belted Kingfisher - a bird at Laguna Honda Res. 4/20-21, was either a very late migrant or a failed breeder. Only historical records of breeding in SF exist (Lake Merced prior to wholesale development of the lake)
>
> Olive-sided Flycatcher - noted first arrival on Mount Davidson 4/19, on Mount Sutro 4/21 one was noted on a survey point within 100m of last year's nest. Olive-sided flycatcher is confirmed nesting only from Sutro in recent years and last noted breeding on Mount Davidson ~2017. Appears extirpated from Presidio and Golden Gate Park where it once bred as well.
>
> Western Flycatcher - first arrival on Corona Hill 4/24
>
> Chestnut-backed Chickadees - first fledglings of '24 noted being fed by parent on Corona HIll 4/24
>
> Violet-green Swallows - people often ask me "where do Violet-green Swallows nest in San Francisco ?" To date I have yet to find a Violet-green Swallow nest in the City that was in a natural cavity or even a nesting box. All seem to be in openings on or near the roofs of houses. As an example a female was exploring the hole in a soffit vent cover near Pine Lake on 4/15
>
> https://ebird.org/checklist/S168787046 >
> Ruby-crowned Kinglet - last detection was Corona Hill 4/19, these seem to have mostly cleared out
>
> Red-breasted Nuthatch- there's been a notable push of these in recent days. 4/23 one was calling from a street/backyard pine on Evelyn Street a few hundred meters from the edge of Mount Davidson, another was on the Mount above the bowl
>
> House Wren - a singing migrant was the first I've detected locally this spring on Corona Hill 4/24
>
> Swainson's Thrush - since arriving on 4/18, a/the Swainson's Thrush has been calling and occasionally singing from above the LaBica entrance to Mount Davidson
>
> Hermit Thrush - lingering /or perhaps moving through on Mount Davidson as recently as the morning of 4/24
>
> Cedar Waxwings - largest recent grouping was ~230 near Parkside Covered Reservoir 4/19
>
> Pine Siskin - have almost entirely cleared out since a flock of 80-100 was seen on 4/17 on Mount Davidson
>
> Lesser Goldfinch - first fledglings of the year noted 4/24 on Mount Davidson and Corona Hill
>
> Fox Sparrow (Sooty) - last noted on Mount Davidson 4/20, seem to have cleared out. Last two days have also been devoid of Golden-crowns.
>
> Spotted Towhee - multiple territories on Mount Davidson, nest building as of this morning
>
> Western Tanager - first migrant push of this species I've noted this spring (after 10+ wintering locally!), three on Mount Davidson, one on Corona mid-day 4/24
>
> trip report from recent days here:
>
> https://ebird.org/tripreport/226201 >
> Dominik Mosur
>
> San Francisco
>
>
