Boom Chachalaca: The Shorebirds of Coroa Dos Ovos

Well I'm back from Brazil, and excited to start posting again. As I mentioned, the main purpose of my visit to northern Brazil was as part of a project run by David Mizrahi at New Jersey Audubon to band and flag Semipalmated Sandpipers (Calidris pusilla) on their wintering grounds. We had a very successful trip, banding 1600 birds in just 8 days of netting.

Semipalmated Sandpipers on Coroa Dos Ovos

The island we were on was called Coroa Dos Ovos, which is Portugese for Crown of the Eggs. It is a very long sandspit that becomes an island at high tide and connects to the mainland during low tide. There are several species of regularly occurring shorebirds here such as American Oystercatcher, Whimbrel, Willet, Greater Yellowlegs, Sanderling, Red Knot, Semipalmated, Black-bellied, Wilson's, and Collared Plovers, Short-billed Dowitcher, and of course Semipalmated Sandpiper. Interestingly enough, all of these species (except American Oystercatcher, Wilson's Plover, and Collared Plover) can be seen feeding in the mangroves at low tide, a behavior that is very difficult for us to imagine in North America.

The tides in this area are extreme. Low tides expose rich substrate in the mangroves, and create extensive mudflats between Coroa Dos Ovos and the mainland on which the shorebirds forage. At high tides, birds are pushed up into the mangroves and onto the island to roost. It was not uncommon to see Whimbrel and Willet roosting in mangrove trees (weird to those of us used to seeing them in salt marsh)! At extreme high tides, many more birds are forced out of the mangroves to roost on Coroa Dos Ovos.

Whimbrel and Semipalmated Sandpipers roosting in the mangroves

We concentrated our efforts right around the full moon, allowing for the highest tides, and we were not disappointed. Up to 10,000 Semipalmated Sandpipers, and hundreds of Willets, Whimbrels, Sanderling, and Black-bellied Plover, dozens of Short-billed Dowitcher and Red Knot, and several other species of shorebirds and terns were found roosting on the island. We caught sometimes more than 300 birds in a night.

One of the Western Sandpipers we captured – an after second year (adult). Note the dark centers to the back feathers, dark tertials, and little bit of rufous on one or two scapulars (leftover from breeding plumage).

The most exciting part about this was the number of rare shorebirds that could be found in these flocks. While scanning for flagged Semipalmated Sandpipers, I located a Curlew Sandpiper (Calidris ferruginea), and Tom Magarian spotted the first few Bar-tailed Godwits of which we eventually had a high count of 14! We captured a total of 4 Western Sandpipers, and I found one long-billed individual mixed in with the semis once as well.

Curlew Sandpiper

Up until last year there were no records for Western Sandpiper on the Atlantic coast of South America (last year our team minus me caught two). There are not many records for Bar-tailed Godwit for Brazil (not certain of the exact number), but last year the team had the first record for the state of Maranhão with a count of 12 individuals. There are no published Curlew Sandpiper records for Brazil, but we just found out about a photograph of an individual from 2010. That makes our bird the 2nd for Brazil, and the first for the state of Maranhão.