Glossy Ibis Records for Colorado and Neighboring States

The Glossy Ibis (Plegadis falcinellus) first arrived in the New World in the early 1800s.During the twentieth century, this species expanded its breeding range rapidly, extending as far west as Louisiana.Vagrants have occurred throughout the Great Plains and even to California.Colorado's 35 documented Glossy Ibis through 2002 are more than in any neighboring state by at least 40%.These records represent primarily single birds during spring migration; however, recent records include some of multiple birds, as well as one in fall.Timing of these records, the birds' association with flocks of the White-faced Ibis (P.chihi), and lack of nesting sites in Colorado suggest that the Glossy Ibis is continuing its migration outside of Colorado.The increased number of records, increased number of birds per record, and recent reports of potential hybrids in Oklahoma and Colorado also suggest that the Glossy Ibis may be expanding its breeding range west into the Great Plains.The Glossy Ibis (Plegadis falcinellus) is a cosmopolitan species native to the Old World from southeastern Europe to Australia.It probably colonized North America in the early 1800s, with the first record from New Jersey in 1817 (Baynard 1913).During the early 1900s, the Glossy Ibis was known to nest in the United States only in Florida (Bent 1926).Nesting records from other states followed, and by the early 1960s the Glossy Ibis bred along the east coast as far north as New York (Davis and Kricher 2000).Currently, the Glossy Ibis resides permanently along the Gulf coast from eastern Louisiana to Florida and north along the Atlantic seaboard to North Carolina (Davis and Kricher 2000).Its breeding range extends still farther north along the Atlantic coast to southwestern Maine.Members of the order Ciconiiformes (storks and allies) are well-known as wanderers both before and after the breeding season.The Glossy Ibis is no exception.In spite of this species' rather limited and coastal North American range, the Glossy Ibis wanders regularly throughout the eastern United States, with some recent field guides showing a distribution from east-central Texas north to Wisconsin and east to Newfoundland (Sibley 2000, National Geographic Society 2002).Through 2002, Colorado had 31 records of 35 individuals of the Glossy Ibis.Most of these records pertain to single alternate-plumaged adults found during spring migration.This paper examines the pattern of vagrancy (dates and locations) of the Glossy Ibis in Colorado, with reference to neighboring states, probes into possible explanations for this pattern, and notes possible hybrids in Colorado.Identification of the Glossy and White-faced Ibises (P.chihi) has been treated well elsewhere and is not repeated here (see Pratt 1976, Kaufman 1990, Patten and Lasley 2000).For consistency, I use seasonal definitions established by many national and state ornithological publications: spring (March-May), summer (June-July), and fall (August-November) (e.g., North American Birds, Colorado Birds).Additionally, unless otherwise noted, I use only records accepted by the respective bird records committee for each state.

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