Jay J. Rotella

Effects of habitat fragmentation on avian nesting success: a review of the evidence at multiple spatial scales

We reviewed published literature to examine the effect of habitat fragmentation on avian nesting success at three spatial scales (i.e., edge, patch, and landscape scales). We identified 86 relevant manuscripts that provided 117 individual tests of hypotheses regarding the effects of habitat fragmentation on nesting success. Most papers and reviews on this topic have been narrow in scope and have not examined multiple spatial scales. However, our results suggest that the scale at which fragmentation is measured (i.e., edge, patch and landscape) and the duration of the studydo influence the probabilitythat a studywill detect a fragmentation effect. Studies that measured fragmentation at landscape scales and studies conducted over several years were more likely to detect effects of fragmentation on nesting success. A recent review of research on nest predators and habitat fragmentation found a verysimilar scale-dependent pattern; predator effects were more prevalent when fragmentation occurs at landscape scales than patch or edge scales. Based on these findings, we recommend future research on the topic should be conducted at the landscape scale, over several years, and incorporate accompanying work on nest-predator ecology. Correspondingly, conservation actions that limit fragmentation at landscape scales should have positive impacts on nesting success rates and bird populations. # 2003 Elsevier Ltd. All rights reserved.

Population size estimation in Yellowstone wolves with error-prone noninvasive microsatellite genotypes.

Determining population sizes can be difficult, but is essential for conservation. By counting distinct microsatellite genotypes, DNA from noninvasive samples (hair, faeces) allows estimation of population size. Problems arise because genotypes from noninvasive samples are error‐prone, but genotyping errors can be reduced by multiple polymerase chain reaction (PCR). For faecal genotypes from wolves in Yellowstone National Park, error rates varied substantially among samples, often above the ‘worst‐case threshold’ suggested by simulation. Consequently, a substantial proportion of multilocus genotypes held one or more errors, despite multiple PCR. These genotyping errors created several genotypes per individual and caused overestimation (up to 5.5‐fold) of population size. We propose a ‘matching approach’ to eliminate this overestimation bias.

Ecological Causes and Consequences of Demographic Change in the New West

R areas in the American West are undergoing a dra m a tic tra n s i ti on in dem ogra phy, econ om i c s ,a n d eco s ys tem s . Long known as the “Wi l d ” We s t , the regi on has been ch a racteri zed by low human pop u l a ti on den s i ties and vast tracts of u n s et t l ed or undevel oped land (Wi l k i n s on 1993, Power 1998). For most of the 1900s, the pop u l a ti on of m a ny ru ral areas in the West grew very slowly or even dec re a s ed . Because local econ omies were based on natu ral re s o u rce indu s tries su ch as mining, l oggi n g, f a rm i n g, and ra n ch i n g, m a ny re s i dents of the regi on con s i dered con s erva ti on stra tegies on public lands detri m ental to local econ omic devel opm en t . E f forts to establish natu re re s erves and to pre s erve p u blic lands from com m ercial devel opm ent were seen as res tri cting the use of vital natu ral re s o u rce s . In recent dec ade s ,p a rts of that Wild West have given way to the “ New ” West (Ri ebsame et al. 1 9 9 7 ) . People from t h ro u gh o ut the Un i ted States have been migra ting to the Rocky Mountains and the inland We s t . With a pop u l a ti on growth ra te of 2 5 . 4 % , the mountain West was the faste s t growing regi on of the co u n try du ring the 1990s. Su rpri si n gly, rapid pop u l a ti on increases are occ u rring not on ly in urban areas su ch as Denver and Salt Lake Ci ty but also in ru ra l co u n ti e s ,m a ny of wh i ch are gaining pop u l a ti on even faster than urban areas (Th eobald 2000). Some 67% of the co u nties in the Rocky Mountains grew faster than the nati onal avera ge du ring the 1990s (Beyers and Nel s on 2000). Con s equ en t ly, s m a ll cities su ch as Bozem a n , Mon t a n a , and Moa b, Ut a h , a re beginning to ex peri en ce traffic con ge s ti on and s prawl . Some of the ru ral pop u l a ti on growth in the New We s t repre s ents an intra regi onal red i s tri buti on of people from the h i gh plains, wh i ch con ti nue to lose pop u l a ti on (Jo h n s on 1 9 9 8 ) , to more mountainous are a s . Ma ny of the new re s i den t s , h owever, a re in-migrants from other regi ons thro u gh o ut the Un i ted States (Ri ebsame et al. 1 9 9 7 ) . The re s i dents of a ru ra l su b d ivi s i on in a boom co u n ty in Montana might inclu de recent arrivals from big East Coast citi e s ,m i dwe s tern farm s ,a n d the nearest small town . Am ong the in-migrants are reti ree s , we a l t hy young adu l t s , and profe s s i onals in com p uter techn o l ogy, real estate , and other servi ce indu s tries (Nel s on 1999).

DUCK NEST SURVIVAL IN THE MISSOURI COTEAU OF NORTH DAKOTA: LANDSCAPE EFFECTS AT MULTIPLE SPATIAL SCALES

Nest survival is one of the most important parameters in the population dynamics of grassland-nesting ducks (Anas and Aythya spp.) that breed in the Prairie Pothole Region of North America. Grassland habitats used by these species are increasingly threatened by habitat loss and the coincident fragmentation, which may indirectly alter nest survival through effects on predators. Although predators are the dominant cause of nest loss, they are difficult to monitor directly. Thus, indirect analyses of habitat variables are required. Many studies have attempted to address the relationship between fragmentation and nest survival; however, few studies have examined the influence of fragmentation at multiple spatial scales. Understanding how landscape characteristics at multiple spatial scales explain variation in nest survival is important, because no single correct scale is likely to exist for a diversity of landscape metrics. We examined the relationships between habitat variables and duck nest survival (n ≈ 4...

Mallard Brood Survival and Wetland Habitat Conditions in Southwestern Manitoba

Although the primary mallard (Anas platyrhynchos) breeding area in North America has been greatly modified by agriculture, the relationship between habitat loss and mallard recruitment is not well understood. Consequently, we used radio telemetry to estimate brood and duckling survival for 69 mallard broods in southwestern Manitoba, 1987-89, and tested for effects of habitat conditions and hatching date. Annual brood and duckling survival averaged 0.49 (range =0.34−0.70) and 0.22 (range =0.16−0.26), respectively

Nesting effort by wild mallards with 3 types of radio transmitters

Although radio transmitters have been used extensively in waterfowl research for 20 years, effects of these devices on wild breeding mallards (Anas platyrhynchos) are largely unknown. Therefore, we compared various measures of nesting effort for mallards radiomarked with harnessed backpacks, sutured backpacks, and abdominal implants. The proportion of females that nested varied (P < 0.05) by transmitter type: 5 of 9, 16 of 16, and 5 of 5 females nested with harnessed backpacks, implants, and sutured backpacks, respectively. Females with harnessed backpacks initiated fewer (P < 0.0001) nests than birds with other transmitter types and devoted fewer (P = 0.007) days to egg laying and incubation than birds with implants. Our results suggest that studies using harnessed backpacks may underestimate nesting effort, hen success, and recruitment

Opinion Projecting the effects of environmental change on Antarctic seals

Abstract We consider how Antarctic seals may respond to changes in climate, realizing that anthropogenic alteration of food webs will influence these responses. The species considered include the ice-obligate - crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii), Ross (Ommataphoca rossii) and leopard (Hydrurga leptonyx) seal - and the ice-tolerant Antarctic fur seal (Arctocephalus gazella) and southern elephant seal (Mirounga leonina). The data analysed are from long-term censuses of Weddell seals in McMurdo Sound (1997–2006), and of Weddell, fur and elephant seals at Arthur Harbour, Antarctic Peninsula (1974–2005). After considering their responses to recent changes in environmental features, as well as projected and current changes to their habitat our conclusions are that the distribution and abundance of 1) crabeater and Weddell seals will be negatively affected by changes in the extent, persistence and type of annual sea ice, 2) Ross and leopard seal will be the least negatively influenced by changes in pack ice characteristics, although, as may be the case for crabeater and Weddell, population size and distribution may be altered through changes in food web dynamics, and 3) southern elephant and fur seals will respond in ways opposite to the pack ice species, but could also be influenced most immediately by changes in their food resources due to factors other than climate.

Meta-Analysis of Relationships between Human Offtake, Total Mortality and Population Dynamics of Gray Wolves (Canis lupus)

Following the growth and geographic expansion of wolf (Canis lupus) populations reintroduced to Yellowstone National Park and central Idaho in 1995–1996, Rocky Mountain wolves were removed from the endangered species list in May 2009. Idaho and Montana immediately established hunting seasons with quotas equaling 20% of the regional wolf population. Combining hunting with predator control, 37.1% of Montana and Idaho wolves were killed in the year of delisting. Hunting and predator control are well-established methods to broaden societal acceptance of large carnivores, but it is unprecedented for a species to move so rapidly from protection under the Endangered Species Act to heavy direct harvest, and it is important to use all available data to assess the likely consequences of these changes in policy. For wolves, it is widely argued that human offtake has little effect on total mortality rates, so that a harvest of 28–50% per year can be sustained. Using previously published data from 21 North American wolf populations, we related total annual mortality and population growth to annual human offtake. Contrary to current conventional wisdom, there was a strong association between human offtake and total mortality rates across North American wolf populations. Human offtake was associated with a strongly additive or super-additive increase in total mortality. Population growth declined as human offtake increased, even at low rates of offtake. Finally, wolf populations declined with harvests substantially lower than the thresholds identified in current state and federal policies. These results should help to inform management of Rocky Mountain wolves.

Mallard brood movements and wetland selection in southwestern Manitoba

Wetland drainage has heavily impacted mallard (Anas platyrhynchos) breeding areas and decreased the amount of wetland area available to mallard broods. Also, habitat selection by mallard broods is poorly understood. Therefore, we investigated habitat use by mallard broods, monitored habitat availability, and tested for habitat selection by monitoring 29 mallard hens and their broods via radio telemetry in southwestern Manitoba, 1987-89. Habitat availability varied (P 0.10) by broods

Factors Affecting Nest Survival of Greater Sage‐Grouse in Northcentral Montana

Abstract We studied greater sage-grouse (Centrocercus urophasianus) in northcentral Montana, USA, to examine the relationship between nest success and habitat conditions, environmental variables, and female sage-grouse characteristics. During 2001–2003, we radiomarked 243 female greater sage-grouse, monitored 287 nests, and measured 426 vegetation plots at 4 sites in a 3,200-km2 landscape. Nest survival varied with year, grass canopy cover, daily precipitation with a 1-day lag effect, and nesting attempt. In all years, daily survival rate increased on the day of a rain event and decreased the next day. There was temporal variation in nest success both within and among years: success of early (first 28 d of nesting season) nests ranged from 0.238 (SE = 0.080) in 2001 to 0.316 (SE = 0.055) in 2003, whereas survival of late (last 28 d of nesting season) nests ranged from 0.276 (SE = 0.090) in 2001 to 0.418 (SE = 0.055) in 2003. Renests experienced higher survival than first nests. Grass cover was the only important model term that could be managed, but direction and magnitude of the grass effect varied. Site, shrub and forb canopy cover, and Robel pole reading were less useful predictors of nest success; however, temporal and spatial variation in these habitat covariates was low during our study. We note a marked difference between both values and interpretations of apparent nest success, which have been used almost exclusively in the past, and maximum-likelihood estimates used in our study. Annual apparent nest success (0.46) was, on average, 53% higher than maximum-likelihood estimates that incorporate individual, environmental, and habitat covariates. The difference between estimates was variable (range = +8% to +91%). Management of habitats for nesting sage-grouse should focus on increasing grass cover to increase survival of first nests and contribute to favorable conditions for renesting, which should be less likely if survival of first nests increases.