David A. Manuwal

BREEDING BIRD RESPONSE TO RIPARIAN BUFFER WIDTH IN MANAGED PACIFIC NORTHWEST DOUGLAS‐FIR FORESTS

We examined the relative importance of riparian vs. upland habitats to breeding birds by comparing species abundance, richness, and similarity of bird communities in managed Douglas-fir forests in western Washington State, USA. We also examined whether forested buffer strips along second- and third-order streams effectively maintain the pre-logging riparian breeding bird community by comparing species abundance, richness, and turnover among three treatments: (1) unharvested controls; (2) sites that were clear-cut, leaving a narrow (∼14 m) forested buffer on both sides of the stream; and (3) sites that were clear-cut, leaving a wide (∼31 m) forested buffer along both sides of the stream. Deciduous trees, berry-producing shrubs, and other deciduous shrubs less common in adjacent upland forest characterized streamside zones. Despite different vegetation features, riparian and upland habitats did not differ in any measures of bird species richness and composition. No species or species group was more abundant...

The Natural History of Cassin's Auklet (Ptychoramphus aleuticus)

Previous knowledge of the natural history of STUDY AREA Cassin’ s Auklet (Ptychoramphw aleuticus) (see Thoresen 1964, fig. 2) comes primarily Southeast Farallon Island (37”4’ N; 123”) is one of the three rocky islets lying 27 miles west of San from the early anecdotal accounts of Bent Francisco, California. This 40.5-ha granitic island ( 1919), Bryant (1888), Dawson ( 1911)) Dawis sparsely vegetated; the most important plants are son and Bowles ( 1909)) Gruber ( 1884)) Heath Farallon weed (L&h&a ~Gnor), a succulent sand

BREEDING BIOLOGY OF THE RHINOCEROS AUKLET IN WASHINGTON

During 1974 through 1983, we investigated the breeding biology of the Rhinoceros Auklet (Cerorhinca monocerata) at three main colony sites on the coast of Washington: Destruction Island (offshore) and Protection and Smith islands (inland islands of the Strait of Juan de Fuca). Average burrow densities were higher offshore, where the auklets nested on shrub-covered slopes; inland auklets nested on grassy slopes and level areas. Egg-laying patterns varied among years and populations, although initiation dates on all islands were similar. The incubation periods averaged 45 days and ranged from 39 to 52 days. Chicks were brooded, on average, for 3.9 days (range zero to 9 days). On Protection Island, early-hatched young grew more rapidly than chicks hatched at a later date. Chicks on offshore islands were fed a variety of fish, whereas those on inland islands were fed primarily two species. The inland chicks were fed heavier fish loads, reached heavier peak body weights, and were heavier when they fledged than were offshore chicks. Breeding success was higher on the inland colony sites.

Spring and winter bird populations in a Douglas-fir forest sere

Changes in bird species richness, abundance, and guild structure were compared among young (42-75), mature (105-165), and oldgrowth (250-500+ years) and between winter and spring, for 2 years in Douglas-fir (Pseudotsuga menziesii) forests of the southern Washington Cascade Mountains. In winter, bird species richness, diversity, and abundance were all greater in oldgrowth than in younger stands. The most abundant species were the chestnut-backed chickadee (Parus rufescens), golden-crowned kinglet (Regulus satrapa), pine siskin (Carduelis pinus), and red crossbill (Loxia curvirostra). In spring, there were few differences in diversity and abundance along the stand age gradient. Species richness showed a slight increase from young to oldgrowth. The most abundant spring species were the winter wren (Troglodytes troglodytes), western flycatcher (Empidonax difficilis), varied thrush (Ixoreus naevius), hermit warbler (Dendroica occidentalis), and chestnut-backed chickadee. The Vauxs swift (Chaetura vauxi) exhibited the strongest association with oldgrowth in the spring. Seasonal changes in abundance were greater in young and mature stands than in oldgrowth. This pattern was most noticeable among permanent resident species. A more favorable microclimate and probably better foraging conditions in oldgrowth in winter may explain the observed seasonal patterns of abundance. J. WILDL. MANAGE. 51(3):586-595 Even though the importance of the breeding season has been strongly emphasized as shaping bird communities, the winter season may be equally critical (Fretwell 1972), especially in regions where large numbers of species occupy the habitat throughout the year. Seasonal population changes, particularly of permanent residents, may provide an indirect measure of habitat quality. Forests of different age may provide different levels of resources, and therefore, may vary in quality. The published accounts by Raphael (1984) and Raphael and Barrett (1984) provided comparable studies for late successional Douglas-fir forests in northern California. The purpose of our study was to document the seasonal changes in bird community structure within a sere of natural Douglas-fir forests and o speculate on the effects of forest management on bird communities during both the winter and breeding seasons. We express our appreciation to M. Q. Affolter, B. Booth, J. B. Buchanan, C. B. Chappell, M. This content downloaded from 157.55.39.123 on Tue, 18 Oct 2016 06:04:41 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 51(3):1987 BIRDS IN DOUGLAS-FIR * Manuwal and Huff 587 Emers, K. W. Hegstad, A. Hetherington, A. B. Humphrey, D. A. Leversee, R. W. Lundquist, J. M. Mariani, B. R. North, M. J. Reed, B. A. Schrader, and L. A. Willimont for assistance with the fieldwork. N. J. Manuwal, J. G. Dickson, R. W. Mannan, R. W. Lundquist, and J. B. Buchanan provided valuable comments on the manuscript. We thank J. M. Mariani for many long hours of data editing and calculation of detection rates for the winter 1984-85 data, and J. R. Osborne for his computer expertise. We thank U.S. For. Serv. personnel at the Wind River, St. Helens, Randle, and Packwood ranger districts and Mt. Rainier Natl. Park personnel for various assistance. We acknowledge the support of L. F. Ruggiero, A. B. Carey, and F. B. Samson. This study was funded by contracts PNW-83-219 and PNW-84-227 and is Contrib. 44 of the Old-growth Wild. Habitat Res. Pro-

Reproductive Commitment and Success of Cassin's Auklet

Reproductive commitment is the sum of all efforts put directly into the production of offspring (Cody 1971). These efforts can be discussed for birds in terms of the following factors: clutch size, duration of breeding season, number of broods per season, replacement clutches, nesting success, nestling growth rate, post-fledging survival, age at first breeding, and adult survival. Because these factors are strongly influenced by natural selection, one should expect differences in the commitment of birds nesting under different environmental circumstances.

The Incubation Patches of Cassin's Auklet

from the skin and connects to the dorsally mounted transmitter. Second, electrocardiograms recorded from the keel-anchored electrodes during flight have much less EMG interference than those recorded by surface electrodes (fig. 4). The reduced interference may be due to multiple factors. One possible reason may be that the sternum bone shields the keel electrodes from the EMG potentials more effectively than subcutaneous tissue shields surface electrodes. Another is that since the EMG potentials along the keel are determined by the electrical activity in both pectoral muscles, the EMG’ s from the pectorals may tend to cancel out along the keel which separates these two muscles. Third, the electrodes are anchored into the bird’ s skeleton, thus rigidly fixing the distance between them even though the bird is in flight. Fourth,

INFLUENCE OF NICHE OVERLAP AND TERRITORIALITY ON HYBRIDIZATION BETWEEN HERMIT WARBLERS AND TOWNSEND'S WARBLERS

Abstract Hybrid zones between Townsends Warblers (Dendroica townsendi) and Hermit Warblers (D. occidentalis) in the Pacific Northwest are narrow relative to estimated dispersal distances and appear to be moving, with Townsends replacing Hermits. We examined whether the habitat-transition and parental-fitness asymmetry models can explain why these zones are narrow and moving by comparing habitat variables associated with warbler territories in the Washington Cascades hybrid zone. Habitat variables did not differ among phenotypes, suggesting that the habitat-transition model cannot explain the narrow and dynamic nature of this hybrid zone. Habitat characteristics of Hermit Warbler territories did not differ inside versus outside the hybrid zone, also suggesting that this zone is not associated with a region of habitat transition. The lack of difference in habitat use could be the result of comparing variables that are not important to pairing success. However, warblers tended to select territories on west-southwest aspects. South aspects in the southern Washington Cascades are dominated by Douglas fir (Pseudotsuga menziesii) and true fir, which is a habitat selected by female warblers when choosing among territories and males. The parental-fitness asymmetry model does not necessarily make predictions about habitat use within the hybrid zone but predicts the superiority of one parental species over the other. However, if significant overlap occurs in habitat use or niche (as in these warblers), then competition between parental species is likely to occur. To determine whether these species compete, we mapped 12 warbler territories and monitored an additional 94 territories throughout the breeding season and found that all males with neighbors compete for and hold exclusive territories. Thus, the pattern of habitat use and territoriality is consistent with the parental-fitness asymmetry model.

CHARACTERISTICS OF BIRD ASSEMBLAGES ALONG LINEAR RIPARIAN ZONES IN WESTERN MONTANA

Bird populations occupying two narrow, linear riparian zones in Mon- tana were studied in 1968 and 1980. The two areas differed in several vegetative parameters such as vertical layering, riparian width, and canopy cover. Bird densities ranged from 355 to 475 pairs per 40 ha. Riparian width, height of vegetation layers 1 and 2, and cover in layer 2 were the most significant variables in male territory location for some bird species. Some species such as the Winter Wren and American Redstart were absent in 1980 from one study area, whereas the populations of most other species were similar between years. Although there have been many studies dealing with the relationships between bird communities and vegetation structure, few have been conducted in narrow, linear ri- parian zones in coniferous forests. Such riparian zones usually have a more diverse bird community, significantly higher total bird density, and more breeding bird species than are found in the surrounding forest (Stevens et al. 1977). During an earlier study (Manuwal 1968) I was impressed with the observation that although the two riparian zones reported in this study were very similar in the general types of vegetation and structural features, there were substantial differences in breed- ing bird species composition. This study was conducted in an attempt to determine why such differences in the avifauna existed. To accomplish this, I tested the hypothesis that bird species richness and density are proportional to the complexity and extent of riparian vegetation. STUDY AREA AND METHODS I conducted this study at Elk Creek and its tributary (the North Fork of Elk Creek) which are located in the Lubrecht Experimental Forest, approximately 64 km NE of Missoula, Montana. The surrounding coniferous forest was a typical mixture of ponderosa pine (Pinus ponderosa), lodgepole pine (P. contorta), Douglas-fir (Pseudotsuga menziesii), and western larch (Larix occidentalis) (Manuwal 1983). I sampled vegetative cover by placing 1-m2 quadrats made of plastic PVC tubing every 30 m along a transect paralleling each side of the creek. At each sample point I recorded percent cover and height of vegetation layers in a vertical column above the quadrat, the species of trees and shrubs (> 1 cm dbh) nearest the quadrat in each cardinal direction, the height of taller trees inter- cepting the sampling column, and width of the riparian strip. I measured the latter two variables with a range finder. I used the spot-map method (Williams 1936, Hall 1964) to determine territorial male density and delineate territory boundaries. I marked the riparian strips either with numbered lath stakes (1968) or numbered plastic flagging (1980) to facilitate the mapping of the exact location of each bird on a map of the study areas.

Bird Populations in Montana Linear Riparian Areas at 12, 28, and 40 Year Intervals

Abstract In 2008, I surveyed bird populations in two riparian areas in western Montana using territory-mapping and compared the results with surveys done in 1968 and 1980. Bird populations were assessed by mapping territories of singing males. Overall vegetation height of the ground layer increased between 1980 and 2008. A major vegetation component, mountain alder (Alnus tenuifolia), suffered massive mortality due to a freezing event in February 1989. The death of the main trunks and re-sprouting of mountain alder changed the structure of the riparian vegetation. Mean height of alder was 1.4 m less in 2008 than in 1980 along Elk Creek. It was 3.4 m lower along the North Fork. Based on male habitat-use information collected in 1968, these structural changes may have negatively impacted the Hammonds Flycatcher, Warbling Vireo, Yellow-rumped Warbler, and American Redstart since males of these species were documented in 1968 to primarily use the upper level of the alder canopy for singing. The MacGillivrays Warbler may have benefitted from the change in alder structure. Bird species richness was similar over time. On Elk Creek, the Willow Flycatcher, Veery and Red-eyed Vireo disappeared, whereas the American Redstart declined from 19 territories to two in 2008. On the North Fork, the Warbling Vireo and American Redstart disappeared and the Hammonds Flycatcher declined from 10 territories (in 1980) to 2.5 in 2008. Bird population size and species composition varied between the two riparian areas. Riparian width of Elk Creek was significantly larger than the North Fork and this corresponded with higher bird species richness and abundance.

Progressive Territory Establishment of Four Species of Neotropical Migrants in Linear Riparian Areas in Western Montana

Abstract We documented settling patterns for territorial males of four species of Neotropical bird species in three riparian study areas in western Montana in 1968, 1980 and 2008. The species were Hammonds Flycatcher (Empidonax hammondii), Warbling Vireo (Vireo gilvus), American Redstart (Setophaga ruticilla), and MacGillivrays Warbler (Geothlypis tolmiei). Early arriving males selected areas with some different vegetation attributes than later-arriving males. The most important vegetation variables in early territories were riparian width, red-osier dogwood (Cornus stolonifera) canopy cover, and red-osier dogwood height. Habitat in territories had some vegetation attributes different than unoccupied areas. Unoccupied habitat had narrower riparian width, taller conifer canopy cover, and shorter dogwood canopy cover.