Chihuahuan Raven

Chihuahuan Raven

Two days ago, while counting a line of Turkey Vultures migrating over Cardel, Veracruz (Mexico), my co-counter Irving excitedly called out a "cuervo!" or raven, something we don't see every day here. The line was more or less overhead and not terribly high, so it was easy to pick out the bird's different shape and snap a few pictures of it.

Chihuahuan Raven migrating with Turkey Vultures

It clearly looked like a raven, but appeared a little smaller and subtly differently proportioned than the familiar Common Raven. The tail was rounder, not as wedge-shaped as in Common Raven, and the head projection was smaller.

Thus we determined it to be a Chihuahuan Raven, a lifer for me, and evidently a short-distance migrant that more commonly winters north of here.

Chihuahuan Raven range map courtesy of ebird.org

In fact, once our sighting has been processed by eBird, it will likely be the southernmost record in their dataset.

same range map, zoomed in, courtesy of ebird.org

The current southernmost records in their dataset are from western Mexico. On the east coast, eBird has not had any records further south than Poza Rica, Veracruz - about 150 km north of here. So really not that far north, then. 

Prairie Falcon

adult Prairie Falcon (photo by Lynn Schofield)

Last Friday, I went with Lynn and two visiting Dutch birders, Leo and Dick, to the highlands around Perote, Veracruz, where we observed this Prairie Falcon.

We were driving along a power line, scanning the surrounding fields, when the car was stopped and I was informed by Lynn that there was my lifer raptor. Peering out the window on her side, I spotted a distant bird that superficially looked like a Turkey Vulture. I studied it intently for a few seconds, lowered my bins and said, somewhat disappointed, "I think it's a Turkey Vulture." At this point my attention was drawn to a bird much closer, and quite happily I confirmed the initial assessment that here, indeed, was the last North American diurnal raptor I still needed for my 'life list'. What a great bird!

Robert Straub in his Site Guide to the birds of Veracruz mentions this species as a possibility for the site, and there is a 1999 record in eBird for the Perote Valley. Whether this bird winters here incidentally or more regularly is hard to say; observer coverage is thinner here than in the US. The Global Raptor Information Network calls it a "fairly common to common transient and winter visitor from October to March, ranging as high as 2,500 m, in Baja California and in Sonora and Tamaulipas and in the interior south over the plateau to eastern Jalisco and northern Hidalgo."

Sandhill Crane in Chichicaxtle!

Sandhill Crane with Wood Storks, 4 October 2011, Chichicaxtle

Yesterday we counted more than 400,000 raptors on migration here in central Veracruz, Mexico. Incredible as that may sound, this is not unusual for this location - in fact, this is an expected number for this count this time of year.

What is unexpected, however, is a Sandhill Crane this far south. I photographed this individual in a flock of Wood Storks yesterday afternoon in Chichicaxtle.

map courtesy of ebird.org, Cornell Lab of Ornithology

As far as I can tell - and I'm looking at this map from eBird - this will be the southernmost record in their dataset after I submit it and after their editor accepts it. I don't know if any other records have been reported this far south, for example in North American Birds.

Predicting big flights

Broad-winged Hawks soaring over Chichicaxtle (including one dark morph)

The raptor migration season here in Veracruz is now in its middle, high-volume part, with flights typically of 30,000 raptors or more each day (see hawkcount.org). The average day count over the last week was just over 76,000. The majority of the flight in this part of the season is of course broadwings.

the direct line measures 966 km, but that is not how the broadwing flies (image courtesy Google Earth)

I mentioned the Corpus Christi hawk watch in my previous entry, and we often look at their numbers to get a sense of what's on our doorstep. That site is located in Hazel Bazemore Park, just outside Corpus Christi, TX, about 1,000 km north of us - as the broadwing flies (their numbers are also posted to hawkcount.org).

Yesterday, the counters in Texas had a phenomenal day with more than 100,000 broadwings counted as migrants. Broad-winged Hawks migrate "up to 400 km / day in Central America" (Smith 1985, cited in Goodrich et al. 1996), or "500 km in 6 hours of ridge flight with favorable winds" (Kerlinger 1989, cited in Goodrich et al. 1996). A thousand kilometers then would probably take them 3 days or so.

September 2011 day totals for Broad-winged Hawk from Corpus Christi and Veracruz (source: hawkcount.org)

Wondering if such a traveling speed could be detected in a direct comparison between the daily counts of both sites, I decided to graph that out. I took daily totals of broadwings for both sites for September 2011. Note that the VRR (Veracruz River of Raptors) totals are really from two count sites combined: Cardel and nearby Chichicaxtle.

Obviously, weather events between southern Texas and central Veracruz will influence the broadwing flight between the two locations.

The Corpus Christi count reported their first larger broadwing flight on the 19th of September. Three days later, we had our first wave. From 21 through 24 September, CC had good sustained flights of broadwings. We (VRR) had two good days (23 & 24 September) and after that flights around the 40,000 mark.

The day after tomorrow, will we register the peak flight of broadwings that they had yesterday?

Cited literature:
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