No one had endeavored to count nocturnal birds before.
To account for unknown species of birds found in the 1997 count.
To complete the species checklist for the Galvan Ranch.
To verify the existence of 28 tropical species in the 1997 count.
To account for all known migratory species absent in the 1997 count.
The Texas population spontaneously migrated to Arizona.
Destruction of the Rio Grande River Valley.
Brush clearing between 1920 and 1945 destroyed the birds' habitat.
Land development between 1990 and 1995.
Failure of the U.S. Fish and Wildlife Service to add the bird to the Endangered Species list.
Clerical error on the part of the U.S. Fish and Wildlife Service.
The ferruginous pygmy-owl was not known to exist in Texas after 1989.
The species was abundant throughout the Lower Rio Grande Valley.
The species was added to the endangered list, based on the status of the Arizona population, but the bird is protected throughout the United States.
The population had spread to Texas counties where the bird had not previously been counted.
It was the first survey of breeding and migratory birds in the Lower Rio Grande Valley area.
It demonstrated that tropical species were fleeing their natural habitats.
It demonstrated that most of the species living in southern Texas were native to the area.
It demonstrated that brush clearing in the 20's and 30's had not destroyed avian habitats in the Lower Rio Grande Valley.
It proved that the ferruginous pygmy owl was still living in Texas.
Tropical birds are being forced from their natural habitat due to the destruction of the rainforests.
The Lower Rio Grande Valley is part of the birds' migratory pattern.
Overpopulation of the tropical species in their natural habitat has forced the bird to migrate northward.
The tropical species were misidentified.
The birds were carried to the area as "stowaways" on commercial transport vehicles.
Grew from less than three to 16.
Migrated to Texas.
The pygmy owl must have migrated to Arizona when its habitat was cleared.
The pygmy owl preferred Texas.
The pygmy owl's habitat includes northern Mexico.
The pygmy owl's probability of survival is higher in the woods than in the desert.
The pygmy owl may have originated in the tropics.
To see if the Texas and Arizona populations had combined.
To count the increase in the bird population.
To determine whether the pygmy owl is migratory.
To determine whether the species requires Federal protection.
To learn more about its nocturnal habits.