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The Peregrine Fund Notes From The Field
South Texas Aplomado Falcon update, April-May 2010
Paul Juergens — in Aplomado Falcon Restoration    Share

As of 14 May, Brian Mutch, Angel Montoya, and I completed the 2010 Aplomado Falcon occupancy survey in South Texas. Tom Cade and Grainger Hunt also visited during the first full week of surveying in the Laguna Atascosa National Wildlife Refuge area. Overall, the results are very similar to what we have observed the last two years.

The falcons looked great, and it was a relief to see the area recovering from one of the most severe droughts on record. Brian and I arrived in South Texas in a torrential downpour, and Angel and I left the area in very similar weather. However, the weather during the survey period was quite favorable, especially during the first three weeks. During the last week of surveying, warm winds out of the southeast and high humidity were the norm. We did make good use of our ATVs early in the survey; although by the end of the survey, all of the roads had dried out and we were able to drive the trucks pretty much anywhere we needed to go.

Work in the Matagorda Island National Wildlife Refuge area, which includes San Jose Island, also went very well. Regarding areas accessed, we did not make it to one of our territories this year in which access requires a boat to ferry ATVs across an arroyo to an isolated unit of the Laguna Atascosa refuge. We usually get assistance from the refuge, but even after several attempts to get the biologist and manager to schedule the boat ride we needed, the refuge ultimately was not able to assist us. We did pick up a new territory off of Old Port Isabel Road north of Brownsville, which is why the number of surveyed territories is the same as last year.

During a survey period of 17 April to 13 May, we observed 82 falcons. This includes 32 pairs and 18 individuals (10 adult females, 2 juvenile females, 1 unknown female, 2 juvenile males, 2 unknown males, and 1 unknown falcon). We surveyed 40 territories of which 32 (80%) were occupied. Here are the results for each survey area:

Total territories surveyed: 40 (MINWR – 16; LANWR – 24)
Total occupancy: 32/40 (80%) (MINWR - 14/16, 88%; LANWR - 18/24, 75%)

Most of the pairs observed were at some point during the survey incubating eggs (11 LANWR, 9 MINWR) or brooding young (1 LANWR, 2 MINWR). One pair observed incubating early in the survey in the LANWR area had failed for unknown reasons; 8 pairs were at the very least observed at a nest site and many times hunting cooperatively, copulating, etc. Again this year, we observed unpaired female falcons in the LANWR area. Generally, this was the same situation as the last two years, however many of the territories that had only females last season are occupied this year and others that were occupied last season had only females present this year. Also of interest, three occupied territories in the LANWR area had juvenile males present. The new structures were found favorable by some of the falcons in both survey areas.

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