November 24, 2005: (Note: the final audited data is below).
I finished compiling the 2005 Hornsby Bend hawkwatch data and wanted to let everyone know how it compared to the previous four years. I was also interested in finding out what the Corpus Christi (ninth year) and Smith Point (12th year) hawkwatch results were. First off, I would like to thank Hornsby Bend Bird Observatory and the Austin Water Utility Center for Environmental Research for running the hawkwatch again this year and the Travis Audubon Society for funding it. Without them we would be missing out on valuable data for central Texas raptor migration. I would also like to thank Peg Wallace and Jeff Hanson for their helpful knowledge and everyone else who spent some time combing the skies with me.
Starting off with total numbers and species numbers, we ended 2005 with a total of 4,173 total migrating raptors. This was the lowest ever recorded for the Hornsby Bend Hawkwatch. The last three years have been between 11,000 and 17,000, which would put us at about one half to one third our average total numbers. Only the first year (2001) was similar at 4,208. For total species we had 17 different raptor species recorded this year, which is consistent in that every year has always been between 16 and 18 total.
Next, I wanted to look at what were the main differences in numbers compared over the past years. The greatest factor in decreased numbers was the missing Swainson's hawk migration over Hornsby Bend. When the yearly average is 8,000-11,000 and we only had 1190, it makes up most of the decline from years past. 2001 had only 2104 Swainson's which is why that years total migrants is similar to 2005. Also notable species, which were down in compared to years past, are Mississippi Kites (77), which has averaged around 350 the last two years. Sharp-shinned hawks (14), which averaged around 80 the last three years. American Kestrel (19), which has averaged about 60 over the last four years. Peregrine Falcon (2), which has averaged about 10 over the last four years. Notable exceptions are Broad-winged hawk, Turkey Vulture, Black Vulture, Osprey, Merlin, and Red-tailed hawks, which stayed consistant with past years. Broad-winged Hawk, Turkey Vulture, and Black Vulture numbers were only surpassed by last year.
After conferring with the Corpus Christi and Smith Point hawkwatches, I have found their results to be similar. Their total numbers way down due mainly to missing Broad-winged hawks, which makes up their greatest numbers. In variable results Corpus Christi also had the highest numbers on record for many of the falcons, rarer hawks, and Mississippi Kites.
Finally, I would like to conclude with some possible reasons for the large decrease in total numbers this year. The arrival of hurricanes Katrina and Rita during the height of raptor migration would seem to have affected numbers throughout Texas. The record high heat for the last few weeks of September, added with a lack of cold fronts may have pushed Swainson's migration to the west of Austin. Did the heat also cause the raptors to soar higher in the sky making the smaller birds like the Sharp-shinned hawk and the fast moving Mississippi Kites harder to spot? The more years we collect data, the more we may be able to understand raptor migration, but also the more questions which will be brought up that we would like to answer. Until next year,-Gary Newgord