Stilt Sandpiper

As most birders know, extreme weather events sometimes bring unusual birds. At Sandy Hook, it rained almost continuously for the last 48 hours; when today the weather finally cleared, there was this Stilt Sandpiper. I found the bird together with a Greater Yellowlegs in an enormous puddle near the hawk watch platform this morning. That puddle has been there since the previous storm more than two weeks ago, and had been slowly shrinking. This morning it was bigger than ever, and made for improvised shorebird stopover habitat.

Stilt Sandpiper is a shorebird that's fairly common on the East Coast in fall migration - which for many shorebirds starts midsummer. In spring, many species, including the Stilt, choose a more inland route, and are rare this far north on the Atlantic.

The majority of Stilt Sandpipers winter in central South America, with smaller numbers wintering from the Salton Sea and locally on the Gulf Coast and in southern Florida further south. First arrivals on inland migration stopover sites are late March for the southern states, but their numbers typically peak mid-April to early May. On today's bird, a few retained juvenile lower scapulars indicate that it was a younger individual.

Both sandpiper and yellowlegs did not stay long; a few hours later they could not be relocated.

The regular hawk watch was, not surprisingly, uneventful. Raptor migration should pick up the next two days, with birds riding a warm front.

Piping Plovers

Here on Sandy Hook it's been raining more or less continuously for the last 48 hours, effectively bringing any landbird migration to a complete stop. Supposedly, once this weather system clears out, there's a warm front with higher temperatures, plentiful sunshine and light west winds to replace it. I expect migration will slowly pick up during the rest of the week, and by Friday we may be looking at Pine Warblers and Blue-gray Gnatcatchers around the platform, and maybe a hawk or two overhead. But today I have a series of Piping Plover shots from last Saturday, when it was bitterly cold but still sunny.

This bird is most likely an adult male, in breeding plumage. The breast band and band on the forehead appear black. On an adult female, these are slightly duller, but the differences are not very pronounced.

Same bird seen from the other side. Note how the breast band looks less black - 'more female-like' actually - than in the previous photos. The head band curves more in a point from this side too, but I'm telling ya, it's the same bird.

Here's a head-on shot of that bird.

It was busy feeding, but occasionally would cock its head up to keep an eye out for predators.

Here it's got a small marine worm of some kind.

In this shot, we see some social interaction. These birds probably arrived fairly recently (one or two weeks ago), and are still a few weeks away from being on eggs. At this stage, they are probably pairing off. Here our male charged at what is presumably another male (only half visible in the frame), running with raised mantle feathers and spread tail while whistling. Standing nearby, a bird molting from winter to breeding plumage, and a bird largely in winter plumage still.

Here's a closer comparison of those breeding and winter plumages. The bird on the right is the same male as in the pictures above. It seems to be finished or almost finished molting its body feathers to a breeding plumage. The bill too, black in non-breeding plumage, is nicely bi-colored black and orange. The bill of the left bird is still largely black, with only some orange starting to appear at the base. The breast and head bands too are just starting to blacken: this bird has just started its molt from winter to breeding plumage. Note how worn the wing coverts are. These are not replaced during the pre-alternate (pre-breeding) molt, and are quite worn on all Piping Plovers right now. These feathers will be replaced during the prebasic molt, in late summer or fall.

Flight picking up

This is one of at least three Cooper's Hawks that were working the northern half of the Hook today. I doubt that they migrated out of the area today, and expect to see at least one of them again tomorrow.

Raptors that were moving in today's stiff NW-winds, included 6 Osprey, 2 Bald Eagles, and... 3 Peregrine Falcons! Especially those Peregrines were a surprise to me, it seems so early for them. I see Peregrines practically daily on the Hook, often perched in the dunes or working the beach. All three Peregrines today flew north in a straight line, and seemed potential migrants to me. One was way out over the ocean, flying parallel to the Jersey coastline. Another was closer along the beach; this was a (blond) tundrius juvenile - that one quite possibly a winter resident, since this subspecies does winter here and generally stays well into April or May. I put this bird on the count because it went north and because I hadn't seen this individual before.

The resident Osprey still have not returned. Gannet numbers out on the ocean are now rapidly building. I counted only north-flying birds today and got to 130 - practically all in the afternoon.

For me personally most interesting sighting yesterday happened while walking the beach in the mist, not too far off shore, a Pilot Whale. I now regularly see Harbor Seals around Sandy Hook, but this was a first...

Partly cloudy weather with light SW winds are in the forecast for Thursday... Seemingly ideal conditions for migration over Sandy Hook.

Little migration

Besides being just about the cutest little things with feathers, Piping Plovers are also Sandy Hook's 'flagship bird', and one of the rarer North American birds, with an estimated population of only several thousand pairs. I found four of them busy foraging, bathing and preening on the North Beach today.

The bird in the background appeared to be still mostly in winter plumage; the other three birds were in full breeding plumage.

Also on the North Beach today this Savannah Sparrow.

Small groups of Wilson's Snipe were seen flying over the platform each of the last few days.

Also a daily sight now are Northern Gannets, albeit still in very low numbers. The resident Ospreys still have not returned... or have they? Today, a male came flying in from the south, circled and hovered for at least five minutes over one of the nesting platforms, never landing, and then went fishing in the bay, not to be seen again for the rest of the day. Was that a nest owner returning to his nest, or was it a newby checking out real estate?

Little migration was apparent over Sandy Hook today, although a good number of Northern Flickers were seen in the first hour of the count. They were all seen flying northwest, toward the very last wooded patch on the Hook near the Coast Guard station. Later, around mid-morning, quite a few were seen returning from that spot. Probably not a good day for crossing the water then.

A few spring arrivals

This first-year drake Common Eider continues on the bay side of Sandy Hook, as does the Iceland Gull on the North Beach.

Recent spring arrivals seen on the very tip of Sandy Hook have been Purple Martin (today), Wilson's Snipe (yesterday), Eastern Phoebe (several were around yesterday, heard only one today), and Northern Flicker. (This last species is found year-round in the holly forest on the middle part of the Hook; birds seen at the tip are usually migrants.) Tree Swallows were seen practically every day of the count this week, most around mid-week.

In other news: I read here that Northern Gannets started moving north past Cape May last Wednesday. In my previous post I noted that I hadn't seen any gannets here on the Hook yet, which I found strange considering I saw huge numbers here this time of year two years ago. Today I did see three Northern Gannets during the count late afternoon, and later during an evening beach walk two more. They are coming...

Started on Sandy Hook

This week I started the migration watch on Sandy Hook, NJ. I did this count two years ago, when I exposed myself to what seems in retrospect to have been two months of rain and cold with biting east winds coming right off the Atlantic, and long stretches with no birds. Already I feel like this year is going to be different, because today, on what's only the third day of the count, I was able to be on the platform in T-shirt. And there were even some birds to be seen, like this rather pale Red-tailed Hawk.

Best bird today was this immature Bald Eagle. These days a fairly common sight at many hawk watches, but for the Hook still a pretty good bird. Seasonal totals here run between 10 and 20 for this species.

Accipiters (like this Cooper's Hawk) are more numerous at this site.

This is the time for Red-shouldered Hawks to migrate through. Sandy Hook being a peninsular site, many buteos of course don't make the crossing. Today I did see a few going high enough for a serious attempt.

Interesting non-hawks this week included an Iceland Gull on the North Beach and an immature male Common Eider on the bay side, across from the bird observatory's office. Northern Gannets are curiously absent.

GWWA in Honduras

The Golden-winged Warbler, according to BirdLife International (the official Red List authority for birds for IUCN), is currently listed as near-threatened. It has "declined rapidly in southern parts of its breeding range in recent years" (BirdLife International 2009).

Local declines of this early successional specialist "correlate with advancing succession and reforestation, and the invasive range expansion of Blue-winged Warbler Vermivora pinus. Other possible causes of population declines are loss of wintering habitat (especially forest edge and open woodland) through agricultural expansion and clearance for plantations, and nest parasitism by Brown-headed Cowbird Molothrus ater." (BirdLife International 2009).

In light of these declines, it is perhaps interesting - though of course largely anecdotal - to note that we saw quite a few Golden-winged Warblers last winter at our Golden-cheeked Warbler field sites. On this blog I even mentioned that in passing here, here and here.

We ended up seeing no fewer than 16 individual Golden-winged Warblers in Honduras last winter. We found the species at every field site we visited. If you've just tuned in, that means five different field sites in pine-oak forest throughout Honduras. At each site, we described at least five different insectivorous mixed species flocks, one per day, and indeed most of our GWWA sightings were of flock members, i.e. birds we found associating with other insectivorous species. The focus of our field work there was the Golden-cheeked Warbler, but we identified and counted all flock members, for a duration of about four hours per flock, over a total of 25 flocks.

At our first field site, in the forests around La Esperanza, we found 3 Golden-winged Warblers. At our next site, Cusuco, we saw 5. In La Botija, our third field site near the Nicaraguan border, we only found one individual. (Most of our locations there were fairly open situations with limited understory.) In La Tigra, not far from the Honduran capital Tegucigalpa, we encountered 4 individuals, while at our last field site, Monte Uyuca, we found 3.

So how does that compare to previous years? After all, this was the fourth year of visiting the same sites using the same protocol.

Well, as some of you will remember, the previous winter I worked not in Honduras but in Chiapas, Mexico. Another team collected the Honduran data. I have the Honduran site reports from that season, and it appears that at least one individual was seen at every site, for a minimum of 5 birds. I'll try to find out if they had more. The year before that, I was part of the Honduran field team and we certainly did not record the species at every site that year. In fact, we only found it in La Tigra (2) and Cusuco (4). The data of the very first year still exist of course but sadly I no longer have them; a computer crash separates me from that year's data. But if memory serves, we only saw 5 or 6 individuals that year.

So that number of 16 for last winter seems pretty good to me.

The majority of those 16 birds were males. In fact, we saw at least 10 males and at least 1 female; 5 birds were not reliably sexed.

With the very strong caveat that this represents only a tiny sample size, it's intriguing to note the skewed sex ratio, isn't it?

My friend - and principal investigator of this Golden-cheeked Warbler study - Oliver Komar coauthored an article describing latitudinal sexual segregation for migratory birds wintering in Mexico (Komar et al. 2005). This tendency of sexual segregation on the wintering grounds is of course well-known in many temperate zone breeders that are short to medium distance migrants. Far less is known about birds wintering in the tropics. Using specimen records from 35 different collections, Oliver and his coauthors found significant latitudinal segregation in nine species, six of them parulid warblers. In all but one case - Indigo Bunting being the exception - males were found to winter further north than females. A popular explanation for the phenomenon is that it allows the territorial sex - males - to return earlier to the breeding grounds, to set up territories.

Golden-winged Warblers winter south of Mexico, and thus were not included in that study. Their winter range is from Guatemala south through Central America to northern South America. Honduras forms part of the northern half of the winter range.

Neither the BNA account, nor the Peterson Warbler Guide, nor the Warblers of the Americas guide mention anything about sexual segregation on the wintering grounds for Golden-winged Warbler. I assume this phenomenon has not yet been studied in this particular species. Our ratio of 10:1 appears suggestive.


Literature cited:
BirdLife International (2009) Species factsheet: Vermivora chrysoptera. Downloaded from http://www.birdlife.org on 11/3/2010
Confer, John L. 1992. Golden-winged Warbler (Vermivora chrysoptera), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/020
Curson, Jon, David Quinn and David Beadle (1994) Warblers of the Americas: An Identification Guide. Houghton Mifflin Company, Boston & New York
Dunn, Jon L. and Kimball Garrett (1997) A field guide to the warblers of North America. Peterson Field Guide Series. Houghton Mifflin Company, Boston & New York
Komar, Oliver, B. J. O'Shea, A. Townsend Peterson and Adolfo G. Navarro-Sigüenza (2005) Evidence of Latitudinal Sexual Segregation among Migratory Birds Wintering in Mexico (Evidencia de la Segregación Latitudinal Sexual en Aves Migratorias durante el Invierno en México). The Auk, Vol. 122, No. 3 (Jul., 2005), pp. 938-94. Stable URL: http://www.jstor.org/stable/4090598