Written by Michael Wilson
July 1, 2010
For the fourth consecutive year, volunteers from across the United States set-out into the night to conduct nocturnal survey routes for the U.S. Nightjar Survey Network. The U.S. Nightjar Survey Network is a national program specifically designed to gather population distribution and trend data on the group of species like whip-poor-wills, common nighthawks, common poorwills and their close taxonomic relatives.
Common nighthawk, Comanche National Grassland Area, SE Colorado, photographed by Michael Menefee.
Over the four-year history of the program, volunteers have collected information from 534 routes and counted 2,950 chuck-will’s-widows, 1,447 whip-poor-wills, 1,083 common nighthawks, 475 common poorwills, 429 lesser nighthawks, and 67 common paraques.
These results are remarkable given that volunteers are asked to conduct surveys under some of the most difficult conditions for a national based bird survey. Most of the difficulty lies in the fact that the surveys at conducted at night and only during the brightest moonlight periods of the breeding season lunar cycle. Moonlight has been shown to positively influence nightjar calling rates and hence their detection by the survey program. On some nights, volunteers must wait until 1 or 2 am for the moon to break the horizon before setting out to blaze their survey routes.
Chuck-will’s widow, photographed by Jeff Bouton in Key West, FL. Photo by Jeff Bouton, Leica Sports Optics.
The distribution of 63 nightjar survey routes conducted in Florida over the past 4 years (areas colored orange) within 16-km hexagonal grid cells. See the US Nightjar Survey Network website for more details. Map by the Center for Conservation Biology.
The relationship between the numbers of Chuck-will’s-widows detected on U.S. Nightjar Survey Network routes across a gradient landcover in Florida shows how human land use negatively affects bird abundance. Graph by the Center for Conservation Biology.
A brood of osprey in Mobjack Bay showing a well-fed chick (left) and an emaciated chick (right). The chick on the right would die the following week due to starvation. Work in Mobjack Bay over a 40+ year period has shown that both reproductive rates and food delivery rates have declined dramatically. The decline in provisioning has led to an increase in brood reduction or chick loss due to starvation. Photo by Bryan Watts.