Variation In Microhabitat Use Research Articles

Temporal Variation in Resource Use by Black-Throated Gray Warblers

We studied foraging behavior and habitat use of male and female Black-throated Gray Warblers (Dendroica nigrescens) to quantify the effects of temporal variation on interpretations of avian resource use. Overall, both sexes primarily foraged by gleaning in single-leaf pinyon pine (Pinus monophyla); however, within-season and between-year variation in behavior and habitat use were found for both sexes. Warblers increased use of shrubs from May to mid-June, and decreased use of shrubs and increased use of pinyon pine from mid-June through August, during each year. Use of sagebrush (Artemisia tridentata) and Utah juniper (Juniper osteosperma) varied between years. Sex differences were found in proportional use of foraging maneuvers. Within-season shifts in plant species and habitat use corresponded to changes in arthropod numbers on the plant species used by the warblers, but between-year shifts in behavior did not correspond as closely with changes in arthropod numbers. Temporal variation in microhabitat use resulted from shifts within seasons in the plant species used for foraging, which was associated with temporal changes in food abundance. Our results also demonstrate the importance of considering the effects of temporal scale in studies of bird-resource interactions.

MULTISCALE PATTERNS OF FLOCKING AND ACTIVITIES OF BROWN-HEADED NUTHATCHES

Brown-headed Nuthatches (Sitta pusilla) were examined at two sites in Georgia, United States, during winter to assess spatial variation in mixed-species flock participation and in activity patterns (mainly bark traversing, cone foraging, and seed hammering). Spatial variation was examined at four scales: between sites, between habitat-patch types (pine vs. mixed woodland) within a site, between tree species, and among microhabitats within trees. Intersite variation existed for the proportions of nuthatches that were heterospecifically flocked, and that were performing different activities. These variables also varied spatially within the Whitehall site, as evident both from chi-square tests comparing flocking and activity patterns between pine and mixed-habitat patches, and from maps depicting locations of observations. Additionally, nuthatches at Whitehall differed in their choice of pine species when flocked vs. nonflocked. No evidence was found for variation in microhabitat use between sites, or between flocked and nonflocked nuthatches. The potential for processes that determine the distribution of birds at different scales to influence one another, and the role of flocking and activity patterns in these processes, is discussed. [Key words: scale, birds, habitat selection, flocking, animal behavior, nuthatches, Georgia.]

Temporal Variation in Microhabitat Use and Spatial Relations in the Benthic Fish Community of a Stream

-Patterns of microhabitat use and overlap among five benthic fish species in a fifth-order stream were investigated during two same-year sampling periods characterized by high vs. low discharges. Microhabitat use patterns for Cottus carolinae (banded sculpin), Etheostoma bellum (orangefin darter), E. blennioides (greenside darter), E. maculatum (spotted darter) and E. zonale (banded darter) were similar to literature reports. During high flow, most segregation occurred along a depth/substrate roughness gradient while in low flows segregation was more common along a velocity gradient. Less segregation in microhabitat use during low flow was probably due to differences in spatial overlap. Five species pairs exhibited high spatial overlap (>0.60) during high flow, whereas one pair exhibited this pattern during low flow. Overall, there was a decrease in spatial breadth (13.91 vs. 10.57) and overlap (0.52 vs. 0.36) of microhabitat use during the low flow period.

Temporal Variation in Microhabitat Use by Age-0 Smallmouth Bass in the North Anna River, Virginia

Abstract Microhabitat use by age-0 smallmouth bass Micropterus dolomieu in the North Anna River was quantified from 10 snorkel surveys conducted between May and August in 1990 and 1991. Depth, mean velocity within the water column, substrate, and cover were quantified in 25 larval brood sites, and the same variables (plus focal-point velocity) were quantified at 634 points where dispersed individuals were located. Larvae in broods occupied a wide variety of microhabitats, but after larvae dispersed from brood sites they primarily occupied low-velocity areas with large substrate or cover. During the first 4–6 weeks after dispersal, juveniles continued to use relatively deep, low-velocity microhabitats. Thereafter, juveniles occupied shallower microhabitats with greater focal-point velocities. Fish size was generally not related to microhabitat use within a sampling period, except during two periods when there was a positive relationship between size and depth use. Microhabitat use of the age-0 cohort of sm...

Seasonal and size-related variation in microhabitat use by a southern Victorian stream fish assemblage

Microhabitat use by a stream fish assemblage was examined bimonthly at 51 sites along Armstrong Creek, Victoria, Australia, for 12 months. Five species-river blackfish (Gadopsis marmoratus), short-finned eel (Anguilla australis), short-headed lamprey (Mordacia mordax), and the exotic species brown trout (Salmo trutta) and roach (Rutilus rutilus)-were collected. Because blackfish were abundant, length-frequency data could be used to distinguish three size groups, corresponding approximately to cohorts of Years 0, 1 and 2+. Twenty-seven habitat variables were measured at each site, and these were reduced by principalcomponents analysis to eight major components. Densities of each blackfish size group and of eels, trout and lamprey showed significant correlations with one or more components. The mean preferred water depth of blackfish increased with fish size. Small blackfish could be found in water ranging from 10 to 50 cm deep, but large blackfish were restricted to depths greater than 20 cm and could be found at depths greater than 50 cm. All species showed preferences for water velocities less than 20 cm s-1. There was also a relationship between fish size and the size of shelter available among substratum interstices.

Microhabitat use in a mediterranean riverine fish assemblage : Fishes of the upper Matarraña.

We examined microhabitat use in Barbus graellsii, Barbus haasi, Chondrostoma toxostoma, Rutilus arcasii, and Salmo gairdneri over a 19 month period in the upper Rio Matarraña, Spain. B. graellsii and Ch. toxostoma exhibited non-random microhabitat use during all seasons and preferentially occupied deep microhabitats with heterogeneous substrates. During the majority of seasons in which they were present, B. haasi and R. arcasii occurred in microhabitats similar to those occupied by B. graellsii and Ch. toxostoma. S. gairdneri was over-represented in high velocity microhabitats with erosional substrates. We did not observe any evidence of interspecific interference competition or avoidance. Substrate composition did not appear to affect microhabitat use outside of its covariation with depth and velocity. Seaonal variation in microhabitat use by B. graellsii, B. haasi and Ch. toxostoma was strongly correlated with seasonal changes in microhabitat availability. S. gairdneri, however, occurred closer to the substrate when average velocities were high. Larger B. graellsii and B. haasi sometimes occupied deeper, higher velocity microhabitats than did smaller specimens. Larger B. graellsii also occasionally occurred farther from shelter than did smaller specimens; the reverse was true for B. haasi. Larger Ch. toxostoma sometimes were found farther from both the substrate and shelter than smaller individuals, whereas smaller specimens occasionally inhabited deeper areas with more depositional substrates than did larger Ch. toxostoma. During Late Summer 1985, smaller Ch. toxostoma also occupied microhabitats with higher velocities than did larger specimens. A comparison of microhabitat use for two species present in both upper and lower portions of the Matarraña indicated that most differences in microhabitat use could be attributed to inter-site differences in microhabitat availability. The data suggest, hovever, that both species shifted to more protected microhabitats in the higher velocity site. Assemblage members generally occupied statistically distinguishable microhabitats and could be classified as: 1) high-velocity upper water column (S. gairdneri), 2) low velocity lower water column (B. graellsii, Ch. toxostoma and R. arcasii), and 3) shelter-oriented benthic (B. haasi). The introduction of S. gairdneri during Winter 1984 did not produce microhabitat shifts in any of the native species. Whether or not the native species affected microhabitat use in S. gairdneri is unknown. Interspecific competition for space, however, did not appear to strongly influence microhabitat use among the native species.