Bird and rodent nesting in excavated cavities in Pinon-juniper woodland, southeastern Colorado

• Main Author: Youkey, Donald E.
• Other Authors: Meslow, E. Charles
• Language: en_US
• Published: 2013
• Subjects: Birds > Colorado > Nests; Rodents > Colorado > Nests
• Online Access: http://hdl.handle.net/1957/37636

I studied bird and rodent nesting in woodpecker-excavated cavities in pifion-juniper (Pinus edulis-Juniperus monosperma) (P-J) woodland in southeastern Colorado during the spring and summer of 1987 and 1988. Two related investigations were conducted: one described characteristics of habitat used by birds and rodents nesting in woodpecker-excavated cavities and the other evaluated whether or not birds and rodents were competing for the nest-cavity resource. Seven species of birds and 4 species of rodents were included in the study: American kestrel (Falco sparverius), western screech-owl (Otus kennicottii), northern flicker (Colaptus auratus), ash-throated flycatcher (Mviarchus cinerascens), plain titmouse (Parus inornatus), Bewick's wren (Thrvothorus bewickii), mountain bluebird (Sialia currucoides), white-footed mouse (Peromvscus leucopus), deer mouse (P. maniculatus), pition mouse (P. truei), and woodrat (Neotoma spp.). 1987 was a preliminary year. In 1988, 248 nests were located in 433 cavities monitored, and cavity density averaged 1.5/ha. Western screech-owls nested earlier than all other species (P < 0.001), plain titmice nested earlier than ash-throated flycatchers (P = 0.033), and other species of birds and rodents nested at the same time (P < 0.05). Seven of 19 characteristics associated with nests differed (P < 0.05) among species: 4 of 5 at the cavity-level, 2 of 5 at the cavity-tree level, and 1 of 9 at the cavity-site level. Generally, larger species (kestrels, screech-owls, and flickers) nested in larger cavities and smaller species (white-footed, deer, and pitlon mice, and Bewick's wren) nested in smaller cavities. Characteristics of cavities used for nesting by secondary cavity-nesting species also differed from characteristics of all cavities monitored most frequently on characteristics associated with cavity size. Differences were demonstrated using univariate analysis (Kruskal-Wallis ANOVA) because with the considerable overlap among species, multivariate analysis (discriminant function analysis [DFA]) could not discriminate among species. Management implications include the need to evaluate impacts to the P-J woodland cavity-nesting community before converting the woodland to rangeland, evaluate impacts of logging in higher elevation forests where many of the cavity-excavating woodpeckers breed, and evaluate the influence of the nest-parasitic brown-headed cowbird (Molothrus ater) and the highly competitive European starling (Sturnus vulqaris). In 1988, 95 cavities were manipulated to yield 47 rodent exclusions and 48 bird exclusions. Proportions of these manipulated cavities used for nesting by birds and rodents were compared to the proportions of 83 control cavities used for nesting by the appropriate group of species. Cavities were revisited at 10-day intervals 4 May - 6 August 1988 and evidence of use recorded. The proportions of cavities used as nests by rodents was significantly greater in manipulated cavities than in control cavities (P = 0.0083). Thus, interspecific competition was experimentally demonstrated between birds and rodents for nest-sites in woodpecker-excavated cavities. === Graduation date: 1991