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
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37636 |
| Date | 15 October 1990 |
| Creators | Youkey, Donald E. |
| Contributors | Meslow, E. Charles |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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