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Protection Island, Washington, is one of the most important nesting sites for Glaucous-winged Gulls (Larus glaucescens) in the Puget Sound area. Changes in the numbers and distribution of nests in a Glaucous-winged Gull colony on Violet Point, Protection Island, were tracked from 1980 to 2010. The colony grew steadily until the early 1990s, then declined to about half its former level. The main nesting sites also shifted from the relatively vegetated central and eastern portions of the point to the sparsely vegetated land near the marina, which had previously been almost completely unused for nesting. This shift was correlated with steady expansion of tall grasses on the central and eastern point. The expansion of the tall grass appears to be displacing the gulls, which is an unusual situation. Further, in the early years of this study the edges of the tall grass areas were prime nesting habitats, but these locations were mostly avoided by 2010. We suggest that predation by Bald Eagles (Haliaeetus leucocephalus) may also be affecting the numbers and locations of gull nests and may be the prime reason that few gulls now nest in the edges of the tall grass areas. Together, the tall grass and eagle predation appear to be carrying out a pincer movement which may be forcing the gulls into suboptimal nesting habitat and driving the decline of the gull colony.
In September 2010, 6 species of shrews (genus: Sorex) were collected at a single locality on the Seward Peninsula of Alaska. Such high sympatric diversity within a single mammalian genus is seldom realized. This phenomenon at high latitudes highlights complex Arctic community dynamics that reflect significant turnover through time as a consequence of environmental change. Each of these shrew species occupies a broad geographic distribution collectively spanning the entire Holarctic, although the study site lies within Eastern Beringia, near the periphery of all individual ranges. A review of published genetic evidence reflects a depauperate shrew community within ice-free Beringia through the last glaciation, and recent assembly of current diversity during the Holocene.
In order to conserve populations of woodpeckers in managed forests of the inland Northwest, managers require information about the nest substrates (for example, trees and snags) in which woodpeckers excavate cavities and the habitat characteristics surrounding those substrates. I describe and compare the nest-site characteristics of the White-headed Woodpecker (Picoides albolarvatus), Hairy Woodpecker (Picodes villosus), and Northern Flicker (Colaptes auratus) in burned and unburned logged Ponderosa Pine (Pinus ponderosa) stands of the eastern Cascade Range of Washington, 2003 to 2010. All 3 woodpecker species most frequently excavated cavities in well-decayed snags. In burned stands, Northern Flickers used nest substrates that had a larger mean diameter at breast height (dbh) than those used by Hairy Woodpeckers, and that were shorter in height than those used by Hairy and White-headed Woodpeckers. Northern Flickers also excavated cavities lower in height than Hairy Woodpecker cavities. In unburned stands, flickers used nest substrates with larger dbh than those used by Hairy and White-headed Woodpeckers. Despite these differences, overall similarity among the nest sites of the 3 species suggests that they make similar use of managed Ponderosa Pine stands for breeding in Washington.
In Alberta, Canada, and throughout its North American range, Arctic Grayling (Thymallus arcticus) populations are rapidly declining. As part of monitoring and recovery planning, sampling protocols currently require direction for consistency and cost effectiveness. We assessed whether common sampling techniques, backpack electrofishing and angling, could reliably detect the presence and determine abundance estimates of the species in wadeable tributary streams of the Athabasca River. Additionally, we report on the use of a novel technique, egg-kick surveys, to detect spawning habitat and monitor abundance. Backpack electrofishing and angling with dry flies had the highest detection probabilities, although CPUEs were generally low. Egg-kick surveys rarely detected Arctic Grayling and generally failed as a monitoring tool in our study streams. We found that the size structure of catches were subject to temporal biases (early versus later summer) and dependent on gear type. As expected, angling detected more large fish (>110 mm) and included both juveniles and adults. We recorded about 3.1 times more large Arctic Grayling/km of angling versus backpack electrofishing. Young-of-the-year were more easily detected using backpack electrofishing in late summer (July–August). We were unable to calculate and compare abundance estimates derived from mark-recapture and three-pass removal methods because both techniques generally failed to meet literature-derived criteria and produced unreliable estimates. Our research emphasizes some of the challenges in formulating effective stream sampling protocols for monitoring a declining species characterized by low densities and patchy distributions.
In an ongoing 15-y study concerning population dynamics of Barred Owls (Strix varia) on Bainbridge Island, Kitsap County, Washington, I documented a steep decline in the Western Screech-Owl (Megascops kennicottii) population and a steady increase in the Barred Owl population. From 1995 through 2010, I conducted 358 auditory playback surveys that showed both changes in abundance and spatial distribution of both species on the island. Statewide Christmas Bird Count data from the same time period also reflect an overall decline in the Western Screech-Owl population and an increase in the Barred Owl population. Further, at least 2 other studies have shown Western Screech-Owl to be prey for Barred Owl, also contributing to the body of evidence that leads to a possible correlation between the increasing number of Barred Owls and the decline of Western Screech-Owls.
KEYWORDS: ARU, autonomous recording unit, bioacoustics, great gray owl, nest monitoring, non-invasive methods, presence-absence survey, Sierra Nevada, Strix nebulosa
The Great Gray Owl (Strix nebulosa) is a difficult species to detect because of its remote breeding locations and secretive nature. We used autonomous recording units (ARUs) to monitor nest activity at 6 Great Gray Owl territories from June–July 2006 in the Sierra Nevada, California. We also used ARUs to survey for Great Gray Owl presence–absence status at 15 potential territories from March–April 2007. Each unit recorded 12 h/night (18:00–06:00). In 2006, we recorded juvenile begging calls at 3 sites. In 2007, we recorded adult Great Gray Owl vocalizations at 10 sites. We recorded audible calls during approximately 40% of the nights sampled at locations with owl detections. We concluded that a combination of ARUs and acoustic analysis provides an effective non-invasive method to detect and monitor Great Gray Owls as well as other secretive and nocturnal species.
The breeding biology of the Black Oystercatcher (Haemotopus bachmani) was studied on Triangle Island, British Columbia, Canada in 2003–2011. Breeding density at this remote site was relatively high, ranging from 2.23 to 3.72 pairs/km of shoreline in the 9 y. Most clutches were initiated in the last 2 wk of May, and the annual mean 1st clutch size ranged from 2.1 to 2.8 eggs/nest, values similar to those recorded at other sites. Egg size differed little in clutches of 1, 2, and 3 eggs. Hatching success at Triangle Island ranged from 55 to 87% in 5 y, which is on the high end of the range compared to other sites. Limited data suggested that adult survival rates exceeded 90% per annum, and 43% of individuals banded just prior to fledging survived through at least their 1st winter. Oystercatchers are reliable indicators of the health of coastal ecosystems, and these data comprise a baseline against which future changes at Triangle Island can be assessed.
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