Again Merlins

At the Sandy Hook hawk watch, Merlins were coming left and right yesterday afternoon and this morning; one even briefly landed on the deck's railing for a snapshot!

Alright, I guess the part about a Merlin landing on the platform for a photo I made up, but I did see a good Merlin flight these past couple of days. It's just that I didn't get any good photos so this one, taken last fall at the Cansaburro raptor banding station in Veracruz, Mexico, will have to do.

A couple of posts ago, I wrote about Merlin migration at Sandy Hook his spring, namely here and here. It occurred to me that the wave of migrants I saw in the first half of April was rather unusual, and apparently wasn't seen by any other hawk watch. The last week of April is a more expected time for Merlin migration to peak. Yesterday I had 20 and today 32 Merlins; these are good but certainly not unusual numbers for late April. Take a look at the table I made summarizing Merlin flights in one of those earlier posts and you'll see that today's total of 32 is a more or less normal peak flight on a more or less normal date for this species.

Apparently, the Cape Henlopen hawk watch had strong Merlin flights on Monday (78) and Tuesday (79), a day earlier than my Tuesday and Wednesday flights. I had nothing Tuesday morning, and very little Wednesday afternoon. It seemed like all migrants, including the Merlins, were packed in a bubble that started Tuesday afternoon and spilled over into Wednesday morning.

Why it stopped Wednesday afternoon is anyone's guess: was it because midday the strong wind changed direction from WNW to NW? Or was the whole thing simply a bubble with backed-up birds that had to go on the first rain-free day, spilled over into the second day, and then petered out?

Incidentally, I also had a fairly decent Sharp-shinned Hawk flight today, with 50. I'm expecting that soon as conditions become more favorable for sharpie migration, a lot more will come. If that happens tomorrow, then I'll still catch that flight...

Saturday morning, I'll be catching another flight. To San Salvador...

Blue-gray Gnatcatcher migration

The Blue-gray Gnatcatcher, according to the authoritative Birds of North America, "may be a diurnal migrant" (Ellison 1992).

Having spent some time at various hawk watches in North America, this is also my impression.

Ellison cites a single tower kill record over multiple years of study from Leon Co., FL, and an absence of the species among lighthouse casualties from another study (Ellison 1992), as circumstantial evidence for the bird's status as diurnal migrant.

Yesterday morning, I went out birding before the start of the raptor count at Sandy Hook, because I anticipated encountering the results of a good passerine flight overnight, and indeed I was not disappointed. Large numbers of Palm Warblers, Yellow-rumped Warblers, Ruby-crowned Kinglets, Hermit Thrushes, Savannah Sparrows, White-throated Sparrows, and smaller numbers of Black-and-White Warblers, Common Yellowthroats, Prairie Warblers, Blue-headed Vireos, and Gray Catbirds were found around the hawk watch platform, where only a day before very few of these birds could be seen.

But I didn't come across large numbers of Blue-gray Gnatcatchers yesterday morning.

There were some around, but not noticeably more than the day before. As diurnal migrants, they probably weren't passengers on the previous night's warbler and sparrow express train heading northeast.

In this part of the range, the Blue-gray Gnatcatcher is an April migrant. The first Blue-gray Gnatcatcher for the Sandy Hook Migration Watch this year was seen on April 6. They're still coming through - another small wave was noted today - but the bulk is probably past. This season I've already counted 112 individuals. The graph below shows my day counts so far. The numbers here represent individuals or small groups of birds seen flying over the platform as they head to the northern tip of the Hook.

Graph 1: daily totals of Blue-gray Gnatcatcher at the Sandy Hook Migration Watch, spring 2010. n=112

A strong peak around the 11th, coincidental with a surge in overall diurnal migration across several avian taxa, and a more even distribution around a smaller peak on the 18th, are apparent. Today's count forms a tertiary peak, and it will be interesting to see how many gnatcatchers I will still get.

Graph 2: cumulative hourly totals of Blue-gray Gnatcatcher at the Sandy Hook Migration Watch, spring 2010. n=112

The spring Migration Watch is carried out daily from 9 AM to 5 PM. As Graph 2 illustrates, most gnatcatchers are seen in the morning. The first hour of the count is usually the best, while no gnatcatchers have yet been seen this season during the last two hours of the count. The graph hints at the possibility of strongest gnatcatcher migration occurring between sunrise and the start of the count.

This pattern may be typical for Blue-gray Gnatcatcher migration in this part of their range.

In the fall of 2006, I was one of the counters at the Smith Point Hawk Watch, a peninsular site on the east shore of Galveston Bay in Texas. There, co-counter Heidi Trudell and I witnessed a couple of days with strong Blue-gray Gnatcatcher migration. We didn't keep an exact count of them, but I seem to remember we saw several hundreds a day, sometimes moving in flocks of 15 or 20. The BNA account mentions a peak on the Gulf Coast for late September, and gives as an example a count of 1,000+ on 23 Sep 1989 Nueces Co., TX (Ellison 1992). Our wave of migrants was earlier in the season: I remember there wasn't much else flying except Mississippi and Swallow-tailed Kites. I think they went all day. In Veracruz too, I have seen Blue-gray Gnatcatchers migrate, though not in the same numbers. In fall, it is certainly one of the most common species there. In Veracruz, like Sandy Hook, most gnatcatchers pass through in the morning.

Cited reference:
Ellison, Walter G. 1992. Blue-gray Gnatcatcher (Polioptila caerulea), 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/023

The fickleness of migration

With north or northwest winds and cool weather, who would have thought that today was going to be a good migration day? Granted, it wasn't exactly epic but it was a heck of a lot better than I expected, and until a shower around 10:30, the birding was downright good. For a while I thought I had been warped into some kind of alternative reality, for birders came up to the platform saying "probably not much today, huh?" and I thought 'are you kidding? Just look everywhere around you!'

The shower shut things down, and afterwards it never came back to quite the same pitch.

I thought I had a great kestrel flight on my hands when I had 6 kestrels in the first hour of the count. These birds go all day and are often a more numerous migrant in the afternoon. I ended up with a somewhat disappointing 65. Osprey, surprisingly, came in second, with 23. None of the coastal sites south of Sandy Hook (or I should say neither of those sites) reported any significant Osprey movements over the last couple of days, so where these birds are coming from, beats me. Fort Smallwood Park, a count site in Pasadena, Maryland, had a modest wave of kestrels yesterday. Their last kestrel peak was 25 on the 5th of April - I had 85 a day later. Yesterday they had 17 kestrels - today I had 65. Note how similar those ratios are!

With 13 individuals counted, the Merlin flight today was solid as expected, but nothing more. Curiously, Cape Henlopen Hawk Watch in Delaware - that other site south of here - had way more Merlins these past three days than kestrels: 31 Merlins against only 4 kestrels. How to explain that? Where did today's kestrels come from? Conversely, my early wave of Merlins barely registered with them. Here this Merlin wave occurred between April 6-12, when a total of 64 Merlins passed the Hook. Cape Henlopen had 20 Merlins during that time frame. It's curious and quite fascinating to see these regional differences in migration patterns!

Before the shower, a good number of swallows were pushing through, as well as a couple of Forster's Terns, several Great Blue Herons, a Chimney Swift and a Purple Martin. Other good birds today included Bonaparte's Gull (2), Glaucous Gull (1), Blue-winged Teal (2), Glossy Ibis (2), Wilson's Snipe (4), and Greater Yellowlegs (6).

A number of beginning birders came up to the platform today in hopes of seeing an American Bittern, the bird pictured at the top of today's post. No doubt they had read about bittern sightings here on the listserv, and wanted to see that bird for themselves. More experienced birders, and certainly the Sandy Hook regulars, know that these birds are hard to see. I've seen and heard them occasionally these last couple of weeks, but that's because I am there all the time. You cannot expect to walk up to the platform and be willing to spend 15 minutes max there and see this bird. That's not how it works.

More about Merlins

The bird pictured above is the first Broad-winged Hawk for Sandy Hook this season, which was seen and photographed at the hawk watch today. They seem to be early this year: practically every other hawk watch, including Great Lakes sites like Derby Hill and Braddock Bay, had their first broadwings last week. I felt my count at Sandy Hook was lagging behind a bit, but then Sandy Hook isn't exactly a buteo kind of place anyway.

And I felt better already after looking at historical data for Sandy Hook. First broadwings last year were 6 individuals on April 13. On the exact same date the year before I had the first 9 for the Sandy Hook Migration Watch. In 2007, the first 2 broadwings were seen on April 21, while the first broadwings of 2006 were spotted on April 15. The first broadwing for 2005 was seen on April 19, and the first 3 BW's for 2004 on April 17. In other words, today's two individuals were the earliest broadwings in recent history!

So these birds were early, but not dramatically so.

What seems unusual to me is this continued push of Merlins, which as far as I can tell no other hawk watch is seeing at the moment. Most sites that post their numbers on hawkcount.org are reporting a few Merlins passing through these days. Nobody is reporting the kind of numbers I'm seeing at Sandy Hook.

The BNA account for Merlin cites a 1985 publication in the Journal for Raptor Research by Bill Clark describing Merlin migration along the coast of New Jersey, which found that peak spring migration past Cape May occurs late April (cited in Warkentin et al. 2005). I've dug into the Sandy Hook archives, and they confirm this for the Hook. So, as good as the Merlin flight already has been, it's quite possible - nay, likely - that the majority of them are still to come.

Still, I think it's unusual that only 11 days into April, I'm already at 63 Merlins for the month. Today I had 15, which seems like a lot for early April.

Let's compare that to Merlin numbers in recent years. In the table below, I've summarized for the last 6 years when the peak flight occurred and how many Merlins were seen that day; how many Merlins were seen in the first half of April that year; and how many Merlins were seen that season.

Year	peak flight	total 1st half of April	season total
2010		63
2009	12 on 4/26	12	105
2008	25 on 4/24	15	219
2007	32 on 4/29	16	184
2006	135 on 4/25	61	387
2005	31 on 5/1	0	97
2004	34 on 4/27	13	272

This table shows that the 63 Merlins so far this April are not unprecedented - 2006 was an exceptional Merlin year with similar counts - but quite unusual nonetheless. A peak flight between 25 and 35 in the last week of April seems to be the rule, with exceptions in both directions, last year being the worst and 2006 the best on record.

I'm very curious to see how the season is going to play out for this species, a personal favorite of mine.

Cited literature:
Warkentin, I. G., N. S. Sodhi, R. H. M. Espie, Alan F. Poole, L. W. Oliphant and P. C. James. 2005. Merlin (Falco columbarius), 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/044

Unusual Merlin flight

It's been an interesting week at the Sandy Hook hawk watch. That Swallow-tailed Kite was only the beginning of a number of unusual sightings, followed by a Short-eared Owl, a Tricolored Heron, an early Brown Pelican and a Cattle Egret within the last few days.

But most striking to me this week was an early push of Merlins: 42 over a three-day period! That would be normal for late April, but seems unusual this early in the season. Early April, you'd expect American Kestrel to dominate the flight. And to be sure, they did: 133 within those same three days. But yesterday, the last of the three days, Merlin was actually more numerous as a migrant than kestrel - and that's unusual for early April.

Did other hawk watches record a similar Merlin flight? Well, one of the ones I check especially, Fort Smallwood Park in Pasadena, Maryland did not see this flight. They had a modest kestrel flight on the 5th (25) , I had a better kestrel flight on the 6th (85), and Bradbury Mountain, a coastal site in Maine, had a phenomenal kestrel flight on the 7th (252)! So this wave of kestrels apparently picked up force as it spread northward. But Fort Smallwood until yesterday had only three Merlins for the month of April, while Bradbury Mountain had 9 Merlins on the 7th - the day of their big kestrel flight. So I'm very curious if they are going to see a wave of Merlins tomorrow. Like many eastern sites, they didn't count today, presumably because of poor weather conditions.

A nearby inland site, Montclair NJ, had a similar kestrel flight the same day I had mine: they had 80, I had 85 on the 6th. Given that Merlin is more of a coastal migrant than kestrel, it is interesting to note that they did get a couple of Merlins yesterday.

And just for the record: the picture at the top is of a male Merlin which I photographed last fall in Veracruz, Mexico, not Sandy Hook.

Swallow-tailed Kite

Today at 2:25 PM this adult Swallow-tailed Kite flew past the hawk watch at Sandy Hook. The bird was far away and went by in a matter of seconds, so this is really the only photo I was able to get, before it disappeared into the haze in the direction of Coney Island.

Click on the photo for a bigger view. Some sun glare is visible on the upperside of the left wing, while the right wing's underside shows the white underwing coverts against dark flight feathers.

In the morning, the raptor flight had been disappointing. Around 12:30, the haze suddenly grew thicker and with a cold breeze coming off the ocean, conditions did not seem favorable for a hawk flight. Yet that's when I suddenly started getting a steady stream of birds, practically all flying along the beach. Most of them were falcons and Ospreys; later in the afternoon, harriers appeared into the mix. In only a few hours, I got to 85 American Kestrels, 13 Merlins, 23 Ospreys, 11 Northern Harriers, 10 Sharp-shinned Hawks, 1 Cooper's Hawk, and 1 Swallow-tailed Kite. No vultures and no buteos.

Other interesting sightings included a Raven, a Glaucous Gull, and a first-of-season Cliff Swallow. Later, around dusk, Scott Barnes and I had three Ravens fly over the Hook, and heard an American Bittern.

Stilt Sandpiper continues

Yesterday I thought it was just a one day wonder, but there it was again this morning, in the same giant puddle it was in yesterday. With better light, I was able to get a better shot.

Hawk migration was still relatively light today, although a nice mix of birds was seen, including at least three Red-shouldered Hawks, all immatures. I put 5 on the count today, but since these birds usually fly up to the tip of the Hook and then turn around, I can't really be sure whether I'm counting the same bird or a new individual every time this happens. This particular bird has some damaged primaries and is thus more easily recognizable. One of the other two had just one broken off primary, while the other's flight feathers were undamaged.

South winds and warmer weather should turn on migration a bit more, especially now that it's April. Today that still wasn't very apparent, although late afternoon had a small influx of Tree Swallows and Glossy Ibis. I did see my first butterflies on Sandy Hook this spring today: a Spring Azure, and a Cabbage White, both around the platform.