Saturday, April 2, 2016

Northern Rough-winged Swallows at Sundial Is and the rest of March

In the spring Northern Rough-winged Swallows and female first-spring Tree Swallows can be an identification challenge.  The Tree Swallows go through a molt in their first fall (pre-formative molt)  they then wear into a plumage aspect the next spring that can look much like a Northern Rough-winged Swallow (this plumage is also confused for Bank Swallows).  Interestingly there might be an advantage to this unique plumage.  The first-spring females can be recognized as females by aggressive territorial males and as subordinates by the older females (Stutchbury and Robertson).

I found a small flock of Northern Rough-winged Swallows on Sundial Island today.  You can see the birds lack the sharply demarcated throat of a Tree Swallow.  The brown smudge on the throat contrasts with the nice white undertail coverts. They lack the flank patches.  They fly with a slower more deliberate wing stroke and their call sounds are short, rough prrts.  

In case you need to know where Sundial Is is:  Sundial Island

I was wondering if this Northern Rough-winged Swallow was doing a display.  It was showing its white undertail coverts.  There were 5 swallows in area, I think only one was doing the display. I have thought I have seen white on the topside on these birds before but was finally able to get a photo of what I was seeing. 

If these are displays, it looks like they squeeze their tail closed and push the coverts out.

Other things out at Sundial:

Bushtit and the nest.

I called this a Cooper's Hawk.

My ebird list from today:

Sundial  Island, Multnomah, Oregon, US
Apr 2, 2016 8:15 AM - 1:45 PM
Protocol: Traveling
5.7 mile(s)
Comments:     sunny, light west wind
45 species (+3 other taxa)

Cackling Goose  12
Canada Goose  7
Wood Duck  5
American Wigeon  1
Mallard  6
Greater Scaup  12
Lesser Scaup  12
Greater/Lesser Scaup  6
Bufflehead  4
Common Merganser  4
Double-crested Cormorant  2
Great Blue Heron  3
Turkey Vulture  1
Sharp-shinned Hawk  1
Cooper's Hawk  1
Bald Eagle  5
Red-tailed Hawk  3
Killdeer  3
Greater Yellowlegs  2
Western x Glaucous-winged Gull (hybrid)  1
gull sp.  2
Mourning Dove  4
Great Horned Owl  1
Anna's Hummingbird  1
Rufous Hummingbird  1
Downy Woodpecker  4
Northern Flicker  11
Pileated Woodpecker  1
Western Scrub-Jay  0
American Crow  4
Northern Rough-winged Swallow  5
Tree Swallow  50
Black-capped Chickadee  20
Bushtit  6
Brown Creeper  4
Bewick's Wren  5
Ruby-crowned Kinglet  6
American Robin  40
European Starling  5
Orange-crowned Warbler  2
Common Yellowthroat  19
Yellow-rumped Warbler  3
Dark-eyed Junco  7
White-crowned Sparrow  15
Song Sparrow  5
Spotted Towhee  11
Red-winged Blackbird  15
Brown-headed Cowbird  2
House Finch  5

The past few weeks I have been hitting Sauvie Island a few times, the Sandy River Delta, Tillamook and a trip to Wasco County to search for possible migrant traps for the spring.  Not much exciting but fun experiences nonetheless.

Red-necked Grebe at Tillamook.

 Osprey enjoying the flower garden out on the porch.

Violet-green Swallow at the Sandy River. Very different shape and flight style from the Northern Rough-winged Swallow.

There has been a discussion on OBOL about hybrid sapsuckers.  It was mentioned that the southern race of Red-breasted has a color pattern underneath the red on the neck that when exposed through wear can look like a Red-naped, thus encouraging false hybrid assumptions.  I could not find anything in the literature regarding this on the northern race of Red-breasted, the beast expected in northern Oregon. I decided to look for evidence of this pattern on the northern race. This one seems to show the underlying black mentioned.

Here is the section of the paper that mentions the issue:

"The plumages of the two forms are well described in the literature (Howell 1952: 240-245, Devillets 1970, Dunn 1978), and only a brief summary is given here. The differing head patterns of daggetti and nuchalis are based simply on an interplay between varying proportions of carotenoid and melanin pigments. When carotenoid pigments dominate the barbs of the head feathers, especially their tips, the relative amount of melanin present is reduced and the daggetti phenotype is seen. Conversely, when black melanin pigment is packed into the feathers of the breast and those of the sites of the black head stripes, the nuchalis phenotype emerges. Although only the feathers of the sites of the white head stripes and those of the throat and crown never have black pigment, all sites can have red pigment, especially in the barb tips, except for small lateral stripes at the base of the upper mandible that always remain whitish. However, even in the reddest individuals of daggetti, a reduced quantity of melanin pigment still is present as a narrow dark band in the middle and basal portions of the feathers of the head and breast, forming an underlying "shadow" that is reminiscent of the melanistic breast band, cheek patch, and head stripes seen so vividly in nuchalis. This is easily demonstrated by clipping the tips off the barbs of feathers in the relevant areas of the head and breast. This point is of special significance because progressive wear of the head and breast feathers during the nesting season, caused primarily in adults when they squeeze through the nest opening, exposes increasing amounts of blackish or dusky color and causes normal daggetti to be identified incorrectly as hybrids. The presumption of all earlier authors that hybridization between daggetti and nuchalis is very common has been based on the routine underestimate of the amount of black normally hidden below the red barb tips of the head and breast feathers in daggetti. This problem is perpetuated in even the most recent field guides (National Geographic Society 1983: 269)."

Thanks for the visit and hope to share some more exciting trips soon.  The roads into the east side of Mt Hood Nat Forest just opened a few days ago and another pelagic on the 30th.

Literature cited:

Johnson, N.K., and C.B. Johnson. 1985. Speciation in sapsuckers (Sphyrapicus): II. Sympatry, hybridization, and mate preference in S. ruber daggetti and S. nuchalis. Auk 102:1–15

Stutchbury, B.J., and R.J. Robertson. 1987. Signaling subordinate and female status: two hypotheses for the adaptive significance of subadult plumage in Tree Swallows. Auk 104:717–723

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