Chile 2007 – Two Populations of Shorebirds on One Bay
Recovering from a 24 hour day of work would be difficult for anyone, but our relatively high average age and the cold damp weather make sleeping in our tents a chore. We finished processing the birds from our night of mist netting an hour after dawn. Without exception we rose bone-tired, eyes swollen from the nearly constant wind, our clothes in serious need of washing, but we felt satisfied with our progress and anxious to start the day.
We followed the flock of Red Knots that had gathered at high tide for most of the day. One of our purposes is to collect as many resightings of marked birds as possible. With our team banding in the Arctic, Delaware Bay, Atlantic Coast New Jersey and Virginia, Florida and Bahia Lomas and Allan Baker’s team banding in Brazil and Argentina, there are many banded birds from nearly every important wintering, breeding and stopover location. Much can be learned.
For example we have two populations wintering in Bahia Lomas, one in the west near our camp and another in the east side about 30 km from here. This is not unlike the birds wintering in Florida where we know of at least three populations separated by about 20 -40 km down the gulf coast starting near Tampa Bay. In two years of banding and resighting we found virtually no mixing, birds in Tampa Bay don’t appear to mix with birds from Sanibel Island.
This distribution of wintering population has many different implications in both scientific and conservation terms. If it is true that there is no mixing here in Bahia Lomas, we should determine the areas where both flocks roost and feed and present them through mapping. To do this we are following birds from the roost out to the areas they feed, keeping location with GPS as we go. Our resightings will also tell us the extent of mixing between knots wintering here and the population at Rio Grande, 100 km further south.
On Wednesday night and Thursday morning we mist-netted again and made a modest catch of 22 knots, plus small numbers of Magellanic Oystercatchers, Hudsonian Godwits, Two-banded Plovers , White-rumped Sandpipers, South American Terns, and Kelp Gulls. We had no recaptured knots.
We are assisting the Chilean Sevicio Agricola y Ganadero (SAG) our US Department of Agriculture counterpart, in their Avian Influenza investigation. Christian Osorio, the SAG biologist is swabbing every bird we catch as part of a country wide investigation. Our team has been cooperating with USDA biologists in NJ and Florida in a similar US study. Avian Flu experts are testing shorebirds like knots because they breed in the Arctic where birds from all worldwide flyways intermingle to varying degrees. The New World Red Knot breeds in an area of the Arctic just south of an area where knots that winter in the Old World breed. It is theoretically possible that avian influenza could be transferred between these populations and therefore between continents. To date, all these investigations have shown no evidence that avian flu has been transferred in this way. For the last five years, we have been working in Delaware Bay with biologists from the Southeast Center for Disease Control, and all of the testing has shown no indication of avian flu in Red Knots.