Habitat selection by loons in southcentral Alaska

Abstract

Three species of loons nest in the Matanuska-Susitna Valley, an area 80 km north of Anchorage in southcentral Alaska. This is a region of intense change; its human population doubled between 1980-1990 to almost 36000 people. The Alaska Department of Fish and Game through its Loon Watch Program has monitored 150 to 200 lakes since 1984, half of which are used by loons. Common loons (Gavia immer) nested on lakes of at least 12 ha while Pacific loons (G. pacifica) used lakes as small as 4 ha. Red-throated loons (G. stellata) were found on even smaller ponds. On all waters used by reproductive loons, 89% were connected to other water bodies, 6270 of the shore was appropriate for nesting and 85 % of the area was < 15 ft (4.6 m) deep. This littoral zone comprised habitat for three-spined stickleback fish (Gasterosteus aculeatus), the dominant food source for loons, and supported large macrophyte beds that were used by loons as chick-rearing areas. The effect of human presence on summer loon distribution was dependent on the willingness of humans to accommodate to the needs of loons.

A landscape-scale model of yellow-billed loon (Gavia adamsii) habitat preferences in northern alaska

“…Such connectivity may facilitate the re-supply of fish to lakes that do not support over-wintering or otherwise self-sustaining populations, but be less important for large lakes that are more conducive to self-sustaining fish populations. Lake depth, size, and hydrological connectivity also are related to the presence of common loons (Blair, 1992;Ruggles, 1994), a closely related species that also feeds chicks solely on fish from the brood-rearing waterbody (McIntyre & Barr, 1997). Shorelines with aquatic vegetation, as defined by the Landsat imagery used here, probably include those with patches of emergent vegetation suitable for foraging, those with wet or shallowly flooded land suitable for nesting, and those having a fine-scale (relative to 30-m pixel) interspersion of land and water such as might be produced by nearshore islands or narrow peninsulas.…”

“…On the Colville River Delta in northern Alaska, yellow-billed loons, Gavia adamsii (Gray), typically rear broods on lakes >13.4 ha that have fish, avoid lakes with fluctuating water levels and high turbidity, and nest on low-lying shorelines (North & Ryan, 1989). At more southerly latitudes, lakes used by the closely related common loon, G. immer (Bru¨nnich), compared to unused lakes, were typically larger, deeper, clearer, more oligotrophic, had higher proportion of low-relief shoreline (i.e., <25 cm in height), more fish, more shoreline emergent vegetation, and were more often hydrologically connected by streams (Blair, 1992;Ruggles, 1994). While local studies provide detailed insights into habitat selection, landscape studies provide inferences to vast areas and may elucidate processes obscured at the local scale (Johnson, 1980;Morris, 1987).…”

“…Yellow-billed loons are patchily distributed and rare in northern Alaska ($3300 individuals) and world-wide ($16,000 individuals) (Earnst, 2004;Earnst et al, 2005), and are a Bird of Conservation Concern to the United States Fish and Wildlife Service (US-FWS, 2002). In this study, we examined yellowbilled loon habitat preferences at the landscape scale with a combination of intensive aerial surveys across a large area and existing Geographical Information Systems (GIS) databases of seven habitat parameters thought to be important to loons (e.g., North & Ryan, 1989;Blair, 1992;Ruggles, 1994). Specifically, we used logistic regression to model yellow-billed loon presence in relation to lake size, lake depth, proportion of the shoreline in emergent vegetation, shoreline complexity, hydrological connectivity, distance to river, and distance to the Beaufort Sea coastline.…”

Status assessment and conservation plan for the yellow-billed loon (Gavia adamsii)

“…Although connectivity is generally favorable for loons, lakes on the Colville River Delta that have large connections to a major river channel are susceptible to fluctuating water levels (and often have high turbidity) and are avoided for nesting (North and Ryan 1989); however, lakes with smaller connections that have flowing water only during high water events are not avoided on the Colville River Delta or elsewhere. Similarly, Common Loon presence has been correlated with connectivity at more southerly latitudes (Ruggles 1994).…”

Defining spatial priorities for capercaillieTetrao urogalluslekking landscape conservation in south‐central Finland

“…a group of pedestrians) (Beale & Monaghan 2004a, Geist et al 2005 or react differently to different disturbance sources (Rodgers & Smith 1997, Stalmaster & Kaiser 1997; 2) reaction distances may be less in birds which are less capable of withstanding the effects of disturbance (e.g. those more stressed by low food availability or poor body condition: Gill et al 2001, Beale & Monaghan 2004b; 3) the availability of alternative habitat may affect tolerance of disturbance and hence FID and AD (Gill et al 2001, West et al 2002; 4) direct approaches may elicit greater FID than tangential approaches (Burger & Gochfeld 1981) although the reverse may also occur (Fernández-Juricic et al 2005); 5) many other factors may affect FID or AD, including animal group size (Burger & Gochfeld 1991), stage of breeding (Bauwens & Thoen 1981), prior exposure to disturbance and/or habituation to disturbance (Burger & Gochfeld 1983, Ruggles 1994, exposure to human persecution or hunting (Ferrer et al 1990, Louis & Le Berre 2000, Galeotti et al 2000 or, even, observers' clothing colour (Gutzwiller & Marcum 1997).…”