Competitive relationships of the Common and Lesser nighthawk

TitleCompetitive relationships of the Common and Lesser nighthawk
Publication TypeThesis
Year of Publication1971
AuthorsCaccamise DF
Number of Pages79
Date Published1971
UniversityNew Mexico State University
CityLas Cruces, New Mexico
Thesis TypePh.D. Dissertationpp
Call Number00471
KeywordsAves, Chordeiles, bird, Common Nighthawk, bird, competition, bird, diet, bird, Lesser Nighthawk, bird,distribution, dissertation, dissertations, theses, thesis
AbstractCompetitive relationships and mechanisms for the maintenance of habitat displacement were investigated in the Common Nighthawk (Chordeilesminor) and the Lesser Nighthawk (C. acutipennis) by studying habitat distributions, behavioral interactions, flight mechanisms and food habitats. A one-way habitat displacement results from the exclusion of C. minor from desert habitats occupied by C. acutipennis. Specific adaptations contribute to the competitive superiority of C. acutipennis in desert habitats; these include lack of pronounced territoriality, a slow maneuverable flight pattern, little aggressiveness, and the propensity for wandering great distances in search of food and water. C. minor is highly territorial, is capable of two distinct flight speeds, is highly aggressive, and generally feeds within territory boundaries. Analyses of stomach contents indicated much overlap between the species and similar levels of specialization; however, when, by inference, food became limiting the diet of C. minor became increasingly generalized while diet overlap declined. Arguments are presented to show that C. minor is best adapted to conditions where food is seldom limiting, while C. acutipennis is adapted to conditions where food resources may often be of low density and/or highly dispersed. Evidence indicates that aggressiveness may act to prevent co-occurance of the species in mutually suitable habitats. These aggressive interactions appeared to function in the form of aggressive neglect. In areas of co-occurrence the more aggressive and dominant C. minor spends a considerable amount of time excluding C. acutipennis from its territory. It is suggested that this time and energy is of sufficient magnitude to place C. minor at a competitive disadvantage in areas of co-occurence with C. acutipennis.