Raptor migration at Derby Hill

Broad-winged Hawk

Last week I visited New York, and part of my trip was an excursion to the Derby Hill hawk watch, where I was a raptor counter in 2006 and 2007. I consider those spring seasons at Derby Hill formative in some ways, for these were my first seasonal field gigs in North America, and the first of several hawk watch engagements I've been on. I've counted hawk migration in Michigan, Texas, Florida, New Jersey, Veracruz Mexico, and even in Honduras, where I now live, but it all began at Derby.

Golden Eagle

It was good to see familiar faces, meet new people also, and of course the birding wasn't bad either. Birding in Central America means that I don't get to see Golden Eagle, Rough-legged Hawk or Northern Goshawk on a regular basis anymore, so those were my target species for the trip to Derby. I was not disappointed. I was also lucky to catch a spectacular (500+ both days) Black-capped Chickadee flight along the bluff.

Northern Goshawk

Derby Hill, located in the southeastern corner of Lake Ontario, does best on southeast winds, and as luck would have it, the two days I was there the winds were from that most favorable direction. Such winds push the stream of migrant raptors to the lakeshore, which they then follow, trying to stay close to land where thermals form. Especially the second day started out beautifully with a parade of low-flying Broad-winged Hawks and other raptors. However, with plentiful sunshine and relatively light winds, the inevitable happened: the hawk flight got higher and higher, and birds were seen further and further out over the lake. This is a classic scenario that Derby regulars have observed many times. Gradually, the flight becomes a 'scope flight', in which observers scan just over the tree line in the direction of the lake, occasionally picking up distant kettles that shimmy in and out of vision, and sometimes are barely visible even in the scope. 

Whenever this happens, the locals speak of birds 'cutting the corner of the lake' or 'jumping off at Nine Mile (Point)' – Nine Mile Point being the name of the nuclear power plant 13 km (8 miles) west of Derby Hill. If the thermals, which the SE wind gently blows out over the lake, take the hawks high enough, the distance to the east shore of lake Ontario doesn't seem so threatening anymore, and hawks can bypass Derby.

Back in 2006 and 2007, I remember looking at NEXRAD radar from weather sites and being fascinated to see a hawk flight out over the lake – on radar. We always wondered if this would be visible by an observer on the ground also.

To field test this, my travel companion and I went over to Selkirk Shores State Park on Tuesday afternoon. For about 35 minutes, we scanned the skies toward Nine Mile Point and observed small groups of raptors coming in off the lake. Between 3:00 and 3:35 PM, we observed 15 Turkey Vultures, 1 Osprey, 1 Golden Eagle, 9 Sharp-shinned Hawks, 2 Bald Eagles, 135 Broad-winged Hawks, and 14 Red-tailed Hawks making landfall at Selkirk Shores. Not bad for an afternoon half hour of hawk watching!

But if the observers at Derby Hill cannot see all the birds 'cutting the corner', we in turn probably didn't see the entire flight either.

Here are some radar images from today (28 April 2013), with a very similar weather situation (light SE winds):

The clusters of green dots are groups of raptors flying along the lake shore. We can see them fly over Oswego, but when they get to Nine Mile Point, where the lakeshore topography changes direction, they seem to simply continue in more or less the same direction, passing north of the corner where Derby Hill is located. The birds appear to make landfall between Selkirk Shores and Sandy Pond, after which the stream of green dots changes course and follows a more northerly route, parallel to Highway 81.

At Derby Hill, the official count got to 843 raptors today, and counter Steve Kolbe noted a high flight in blue skies. Here's some more radar imagery, from almost an hour later. From 1:22 EDT to 2:10 EDT, several flight lines are shown: one over the lake, one over Derby Hill, and even some flight south of Derby Hill. The change of direction west along Highway 81 remains visible.

Isn't it incredible that hawk flights can be seen on radar this way? And what about other hawk watches? The NEXRAD radar network covers the entire United States, so in theory it ought to be possible to see these flights for other major hawk migration sites. The thing is: it all depends on how far the hawk watch location is from the nearest radar station.

Think about it: the earth is round, while the beam of the radar is straight. Thus, the radar samples relatively close to the ground in its immediate vicinity, but at higher air strata further away.

Here's a look at a slice of today's radar for Braddock Bay, like Derby Hill a Great Lakes raptor count site with a good spring hawk flight. At the time of writing, they hadn't posted their day totals yet. Around midday, there was only a modest flight visible on radar:



Birds can be seen following the lakeshore east, but the gray and green blocks zip off the screen, presumably as the flocks gain altitude and fly above the radar.

What about Whitefish Point, Michigan? Sadly, that site is at the edge of the range of the nearest radar (in Marquette) and thus radar images for Whitefish show nothing. There may well have been a flight there today, but due to its location relative to the nearest NEXRAD radar, it will never be visible on that radar.

Hawk migration in Honduras

Broad-winged Hawk

These last few days, hawk migration, especially that of Broad-winged Hawks, has been evident here in (southern) Honduras. Most of the time, the wind here comes from the north, but when the weather switches to light south winds late March - early April, migration of broadwings can be expected. We saw this last year also, although a week later.

our wintering Merlin, still around

Roselvy and I first noticed hawk migration this week on Saturday, when we were treated to 11 raptor species (not counting vultures) at our local patch, Laguna Villa Royal. That list included residents such as Common Black-Hawk and Red-tailed Hawk and local winter visitors such as American Kestrel and Merlin. Raptors observed actively migrating included Osprey (3), Mississippi Kite (1), Sharp-shinned Hawk (1), Cooper's Hawk (1), Broad-winged Hawk (111), Swainson's Hawk (1), and Peregrine Falcon (2). Sunday, we observed hawk migration at three different locations along CA-5, the highway that runs from Tegucigalpa south to the Pacific lowlands, for a total of nearly 900 broadwings. Yesterday, the wind shifted to north and picked up in strength, and early morning a few remaining broadwings could be seen struggling in the wind.

First big flights of the season

Broad-winged Hawks

We have now had the first of those 'big days' that the Veracruz River of Raptors is named for: literally a stream of many tens of thousands of hawks migrating overhead. Having counted in this project for a few years now I am not new to it, but it never ceases to impress me.

The last couple of days we've had big flights of Broad-winged Hawk, one of the four raptor species that together make up 99.9% of our count here in Veracruz. (The other three are Mississippi Kite, Swainson's Hawk and Turkey Vulture.) We knew these birds were on our doorstep when we saw the counts in Corpus Christi (Texas) soar last week. We often get what they get - in tenfold. The only exception to that rule appears to be Prairie Falcon, a bird they get annually in low numbers, but we don't get at all.

Broad-winged Hawks

Flocks of more than 20,000 broadwings are not exceptional here in central Veracruz. The flight is often very concentrated, with tens of thousands of birds moving through in only a few hours. Typically, the flight starts in Cardel, then moves further inland to Chichicaxtle, which gets the afternoon flight of soaring raptors. Afternoons in Cardel are usually more laid-back, with falcons, Ospreys and accipiters dripping through.

Exceptionally late Broad-winged Hawk migration

juvenile Broad-winged Hawk

I'm back in El Salvador. Yesterday, I went on a field excursion organized by the Salvadoran branch of Partners in Flight (PIF), the principal club of bird observers in El Salvador. We went to Walter Thilo Deininger National Park near the coastal town of La Libertad, where we saw a fair number of interesting birds - really more than any of us had expected.

By far the most noteworthy sighting, however, was of a group of 17 Broad-winged Hawks - later followed by smaller groups for a total of at least 40 individuals - apparently migrating over the site!

All birds were juveniles.

juvenile Broad-winged Hawks kettling over the park

As far as I'm aware, this late migration of juvenile Broad-winged Hawks has not been previously described - for Central America, or indeed any other site. The species winters in northern South America and throughout Central America; a small number winters in southern Florida and the lower Mississippi Delta and coastal Texas. The majority of birds that winter in the US are juveniles (Goodrich et al. 1996).

juvenile Broad-winged Hawks in a glide over the park

Highly gregarious in migration, the species can be seen in large congregations in the northeastern US during the second half of September, Texas late September, Mexico early October. Fall migrants are noted in Costa Rica and Panama from late September to mid-November, but most pass through in October (Goodrich et al. 1996). 

juvenile Broad-winged Hawk

Separate migration of age classes is well-known during spring migration, when the majority of adult Broad-winged Hawks precede the majority of juveniles by about two to three weeks. In fall, all ages usually migrate together (pers obs).

Flying with the broadwings were single individuals or small groups of two or three Turkey Vultures. This surprised me less, as a small percentage of Turkey Vultures is known to linger and migrate opportunistically. Mexican hawk counters in Veracruz told me it is often possible to see Turkey Vulture movement well into December.

References:
Goodrich, L. J., S. C. Crocoll and S. E. Senner. 1996. Broad-winged Hawk (Buteo platypterus), 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/218

Dots

A couple of posts ago, I grumbled about having seen so little hawk migration thus far in El Salvador.

Last Saturday, Roselvy and I went to a Maya archaeological site called San Andrés, in the Valley of Zapotitán, more or less halfway between San Salvador and Santa Ana. Here, we found beauty, tranquility and, atop "Estructura 4", a 360° view of the sky.

Structure 4 is the hill on the far right in this picture, behind the little tree. The other three hills are Structures 1, 2 and 3, which are off limits. Although not as impressive as Tikal in Guatemala or Copán in Honduras, San Andrés is an interesting place to visit, with remains of human habitation dating back 3000 years. Situated in the Central American Volcanic Belt, its history is one of settlements establishing themselves, growing, flourishing, and then being wiped out by a volcanic eruption, before the whole process starts again.

Between 10 AM and 4 PM, we watched thousands of raptors, mostly hawks and vultures, stream high overhead. In the morning, the flight was dominated by Swainson's Hawks, which can be seen in the picture at the very top. A few broadwings are also visible in that photo.

Turkey Vulture and Broad-winged Hawk were the other two abundant species, both of which can be seen in this picture if you click on it. The hawk on the left is something else, and if you want to try and identify it for yourself, go right ahead. I'll tell you what it is a little further down in this post.

In the afternoon, the flight was dominated by Turkey Vultures, with thousands streaming over. Scattered among them were Broad-winged Hawks, eight of which can be seen in this picture.

Other migrant hawks we noted were Zone-tailed Hawk (2), Mississippi Kite (12), American Kestrel (1) and Sharp-shinned Hawk (1). With non-migratory, resident raptor species Northern Caracara, Short-tailed Hawk and Roadside Hawk, we got to 11 diurnal raptors, two vulture species included. The 'mystery hawk' in the third photo of course is a Zone-tailed Hawk. Only superficially similar to Turkey Vulture, the bird stands out as different from TV's in a number of ways: wingtips pointier and swept back, tail longer and thinner, head bigger. In this photo, the zone-tail looks a lot smaller than the Turkey Vultures, but that's partly because it is flying higher.

To get a sense of where we were seeing all these birds, here is a relief map of western El Salvador. Right in the middle, below a small crater, is San Salvador. The crater belongs to Volcán de San Salvador. The two yellow cards halfway between that crater and a crater lake, called Lago Coatepeque, identify two archaeological sites, one of which is San Andrés.

We saw birds flying mostly due east, which would bring them a little north of Volcán de San Salvador. I posted our sightings to the national birding listserv here in El Salvador, and this yielded a couple more descriptions from people who had seen the same thing.

Cusuco

National Park Cusuco was next on our itinerary for this winter's search for Golden-cheeked Warblers in Honduras. We found two goldencheeks there, one of them again an adult male! This brings the adult male : females/immatures ratio up to 6 : 3, a very unusual and intriguing result so far. In this part of the winter range, you'd expect that ratio to be the other way around.

We also continue to see Golden-winged Warblers, more than in previous years. In Cusuco, we saw 4.

But for us, Cusuco this year was marked more than anything else by what we found in the early morning on January 1: someone had broken into the car, and stolen various items, including Kashmir's passport, which he - foolishly, it must be said - had left in his otherwise empty camera bag. (I'm writing this blog entry in the Mexican consulate in San Pedro Sula, where we are waiting for his replacement passport to be processed.)

In Cusuco, we stayed at the eco-hostel in Buenos Aires. I had stayed there before and had fallen in love with the desolate, magnificent view of the valley below. However, the hostel's peripheral location also meant an additional safety risk, and indeed several items we had left out - hand soap, detergent - were stolen. That, and the incessant rain the last four days or so, made our visit a little less pleasant than it could have been. I remember swimming in a mountain stream there and seeing groups of Swallow-tailed and Mississippi Kites overhead, once with a King Vulture mixed in, but that was two years ago, in February. This time, it was often quite cold, misty and rainy, and looking for mixed species flocks was sometimes difficult. Two days were lost because we were unable to find a flock. Our last flock was hard to follow in the pouring rain on a steep slope.

Today in San Pedro Sula we bought a 'new' (used) window for the car, had it installed, and Kashmir made progress with his passport. Hopefully he can pick that up tomorrow and we can continue to our next field site, La Botija near San Marcos de Colón. That's on the other side of the country, so we have a long drive ahead of us, to what I expect will be much nicer weather, and a bit more comfort. In previous years, goldencheeks were not common at this site either, but we'll see.

Ever since day one, we've had minor but continuous car problems. We now have had all four tires fixed. We've had to deal with a broken thermostat, halting circulation of the engine coolant, resulting in an overheated motor on a hilltop somewhere. Still remaining is a right front wheel suspension issue, which appears to be minor. We do need to buy another tool for replacing tires, because the one we had was stolen on New Year's Eve.

Here are some snapshots from Cusuco.

This is a Spotted Woodcreeper, a fairly common species in Cusuco and a regular flock member there.

Yellowish Flycatcher is another common species in Cusuco.

Common Bush Tanagers travel in tight packs and often appear to associate with mixed flocks, although they are also found in single-species flocks. They are somewhat omnivorous and will eat fruit as well as insects.

This immature Broad-winged Hawk was on something it caught on the road, but flushed as we approached. It landed in this oak nearby, possibly waiting for us to leave so it could return to its prey.

Is this a good season?

We still have about 250-300 hours (or a little less than a month) of counting to do here in Veracruz, but with 2/3rd of the season and nearly 4 million raptors behind us, we have a fair idea how the majority of species did this year. (Please refer to www.hawkcount.org for exact numbers.)

Turkey Vultures for example, currently dominating the flights and clearly not done yet, are fairly numerous this year. We've already counted more TV's than last year and we're almost on a par with the 2006 total. We're now at 1.3 million. Some years the count reaches 2 million, exceptionally more (2.7 mil in 2002).

For Osprey, also still passing through although tapering off, 2009 is already the best of the last 8 years of counting.

Swallow-tailed and Mississippi Kites are early migrants; the last SK was seen on the 29th of September. The last Mississippi's are still passing, but in very low numbers now. The Swallow-tailed Kite had a fairly low season, while the season for Mississippi Kite was a little better than average. The current total of 135 Hook-billed Kites seems about average. Last year's total of 200 was the highest on record. For Northern Harrier this is a low year, although some may still pass. The accipiters also are having a low year, while 6 Common Black Hawks is about average for that species.

A Harris' Hawk was seen yesterday, the third for the season, which is still on the low side. Seen two days ago were 4 Red-shouldered Hawks - all in the same line and passing within 10 minutes of each other - and this makes their total 12, which is a good seasonal total. Numbers of Broad-winged Hawks this season are low, but not dramatically so, as last year. Bad weather in the last 10 days of September probably depressed the count results for that species. For Swainson's Hawk (pictured at top), however, this year is already the best year since 2005, and we're not done yet - they too are still moving through in good numbers. Another buteo that is doing well this season is Zone-tailed Hawk; this is already the second best year on record (only 2007 was better). For Red-tailed Hawk it is still too early to say anything.

This is one of more than 1.4 million broadwings counted this year. This is a juvenile bird.

The falcons were late this year, but we're catching up. We've had some good kestrel flights recently and the seasonal total for American Kestrel is getting there, although still on the low side. For Merlin the season is about average, while for Peregrine Falcon this is already the second best year on record.

In the unusual raptor department, there were of course the birds I wrote about in the previous blog entry. We've now also had a couple of White-tailed Kites in the lines that we presumed were migrants, and a couple of days ago a White-tailed Hawk. Last year we saw resident White-tailed Hawks occasionally from both count sites, and they were a common sight near the raptor banding station. This year they are curiously absent: the bird on the count was the only one seen this year anywhere in central Veracruz that I know of. Last year we would occasionally see resident Crane Hawks, but they too are absent this year. Resident raptors here this year are Short-tailed Hawk, Roadside Hawk and Gray Hawk (all three common), and Laughing Falcon, Bat Falcon, Crested Caracara, Snail Kite and White-tailed Kite (less common).

Yesterday, we also had the following raptor at the Chichicaxtle count site (see photo below). For those of you keen on sharpening their raptor ID skills, I'll discuss it first before telling you what it is. (As always on this blog, clicking on any photo will enlarge it for you.)

The bird was not close, yet close enough to observe various details regarding shape and even plumage in this photo. If you know upon just a glance what this is, you know your hawks pretty well. The counter who saw it first said "John, take a look at this, I have no idea what this is" and when I showed the photo last evening to other counters, they too were puzzled. I actually did know almost immediately what it was, and I'm tapping myself on the back here to make up for an earlier identification blunder yesterday, about which more later.

Well, what is striking about this raptor? The fact that it has short, paddle-shaped wings and a long, banded tail. This bird does not look like any of the raptors found in the US, and indeed it is a tropical raptor. In the field, my co-counter suggested Laughing Falcon, but this bird was bigger than that species, and this bird did not have a facial mask. Instead - and this is not visible in the photo but was visible in the field - the bird had a white collar around the neck. It's a Collared Forest-Falcon. Normally a secretive species that "does not soar" according to Howell and Webb, but there it was in the open, and of course soaring. Every once in a while, a bird will do something outside its normal behavioral repertoire.

So yeah, I was reasonably pleased with myself for knowing right away which raptor this was, especially a species you would not expect to see under those conditions. Earlier that day, though, I was alerted to a group of distant waterbirds, that were provisionally identified as Wood Storks. "Well," I said, intending to sound authoritative, "I think they're [American White] pelicans. Look at how they are kettling, all stacked on top of each other. Wood Storks are usually more level with one another in a kettle." I thought I had made a pretty strong case, and then when they streamed out in a line of long bows, I felt certain these were indeed pelicans, not storks. But as they got closer, they somehow morphed into Wood Storks! I felt like an idiot, for we have seen thousands and thousands of both species now - more Wood Storks than American White Pelicans, but still - and I should know how to tell one from the other. Up close they are very different; from a distance they can appear deceptively similar.


Here's a kettle of Wood Storks - ahem, no, I mean American White Pelicans of course, photographed a few days ago in Cardel...

Update

So much to write about, so little time.

Today a short update on some of the more notable recent sightings from the Veracruz River of Raptor counts in Cardel and Chichicaxtle.

Perhaps the weirdest sighting, and still controversial, was that of a Northern Goshawk on the 4th of October. The bird was in a line, fairly low, that I was counting overhead in Cardel. Irving was scanning this line a little farther ahead, and suddenly came over to me all excited saying "John! John! Take a look at this bird!" At that moment, the bird was directly overhead and for about 2 seconds, I got to look at it, before it disappeared behind the top structure of the hotel. It was obviously a very large accipiter. When I lowered my binoculars, I looked at Irving and said "Goshawk??" That's what it looked like to me, and evidently that was also what it looked like to him. But that's a bird so unlikely to show up here that I remained incredulous for a while. We both saw the bird well, and although the lighting conditions were not sufficient to note plumage details, the shape and the sheer size of the bird - much bigger than any Cooper's Hawk I've ever seen - seemed to point to that species. Of course there are no photos of this bird, and for this reason it will probably remain controversial. Fact is that two competent observers saw this bird not very far and both independently reached the same conclusion. On the other hand, supportive plumage details would have been a lot better. It's a sighting that I personally am not very happy with - it went by too fast to be 100% sure.

I also got to see a Ferruginous Hawk, further away but visible for a longer time. It was in a line I was counting and I almost immediately knew what it was, even though I had never seen one before. I called Rigo, one of the other counters, who looked at the bird through the scope and confirmed the identification. This was on October 7. Another one was seen on October 13.

A couple of Jabirus were seen recently, I don't remember exactly which date. Wish I had seen them; there was one last year and I missed that one. It's a species I have yet to see for the first time.

And only a few days ago, on October 13, a probable Rough-legged Hawk was seen and in fact photographed in Cardel. Two photos were taken of the bird, neither one of very high quality. The photos have been reviewed by various experts and nobody seems to be able to flat out call it a unquestionable Rough-legged Hawk, although most reviewers tend to lean towards that species. I wasn't there so I never saw the bird, I've only seen the photos. The bird in the photos shows carpal patches, but lacks a belly shield - unusual for a Rough-legged Hawk.

Anyway. The photos today are of completely different species. The bird at the top, flying near the moon, is a Hook-billed Kite, while the second photo in today's entry is of a dark morph Broad-winged Hawk. We see them every day and every once in a while, one is low enough to get a decent photo of.

Higher numbers continue

Good hawk flights continue here in Veracruz, with daily totals of at least 70,000 raptors for four consecutive days.

Broadwings and, to a lesser extent, Turkey Vultures dominate the flight this part of the season, while Swainson's Hawks are seen daily in low numbers.

We also had a good Wood Stork flight yesterday, with 3,110 migrants counted. After a long day of travel, these three were looking for a place to spend the night.