Mid-contract management of Conservation Reserve Program grasslands provides benefits for ring-necked pheasant nest and brood survival

Conservation Reserve Program (CRP) fields may provide good habitat for nesting and brood-rearing ring-necked pheasants (Phasianus colchicus) during early stages of succession. But, the success of hens in early successional CRP, relative to late successional CRP and other grassland habitats, has yet to be evaluated. The reproductive period is especially critical for populations of pheasants, and CRP's benefits to hens and chicks may decrease as fields age because of loss of vegetative diversity, decrease in vegetation density, and accumulation of residual litter. During 2005–2006, we evaluated spatial and temporal variation in nest and brood survival for radio-marked hen pheasants in areas of northeastern Nebraska where portions of CRP fields had been recently disced and interseeded (DICRP) with legumes. Nests in DICRP tended to have a higher daily survival rate (0.984; 95% CI: 0.957–0.994) than nests in grasslands (including CRP) that were unmanaged (0.951; 95% CI: 0.941–0.972). The probability of 23-day nest success was 0.696 (95% CI: 0.631–0.762) for DICRP and 0.314 (95% CI: 0.240–0.389) for unmanaged grasslands. Daily brood survival rates varied by habitat type, brood age, and date of hatch. The probability of a brood surviving to day 21 was 0.710 (95% CI: 0.610–0.856). Brood survival rates increased with time spent in DICRP and as the brood aged. Survival decreased as broods spent more time in cropland and peaked seasonally with broods that hatched on 15 June. Brood survival probability, to 21 days, would be reduced to 0.36 (95% CI: 0.100–0.701) if broods in our sample had not used DICRP. We combined nest and brood survival in a productivity model that suggested 2,000 hens, in a landscape with no DICRP, would produce 1,826 chicks, whereas the same hens in a landscape of 100% DICRP would produce 5,398 chicks. Production of first-year roosters more than doubled when hens nested in DICRP. Without DICRP, population growth rates of pheasant populations usually declined; with DICRP, populations stabilized with at annual survival rates of 0.3 or greater. The positive response of nest and brood survival to discing and interseeding CRP provides further evidence that CRP fields must be managed to optimize wildlife benefits. © 2012 The Wildlife Society.     

Home range and habitat selection of northern bobwhite coveys in an agricultural landscape

Northern bobwhites thrive in fine-grained landscapes with a diversity of early succession woodland, grassland, and agriculture-associated habitat types. Bobwhite conservation has proved challenging in the increasingly coarse-grained Midwestern landscape as simplified agricultural cropping systems are implemented at larger spatial scales. Regardless, managing agricultural landscapes on private lands is the primary opportunity to restore bobwhite populations in the Midwestern United States. Although bobwhite habitat requirements are well understood, habitat selection in contemporary Midwestern landscapes is not well understood, especially on private lands where populations are declining. We used compositional analysis to investigate second- (study area) and third- (home range) order habitat selection by radiomarked bobwhite coveys on 4 private land study areas in southwestern Ohio. Mean covey home range size was 26.1 ± 2.2 ha (n = 48). Although home ranges were established in areas with more grassland cover, bobwhites most strongly selected early succession woody habitat (e.g., fencerows and ditches) at all scales, and selection for grassland diminished between the study area and home range scales. Grassland selection varied among sites and was strongest on sites with more row crop area. Woodlots were avoided at the study area scale, but were selected within home ranges. Grassland cover, like that provided by contemporary conservation programs, is an essential component of bobwhite habitat in the Midwest, but our results suggest more emphasis should be placed on early succession woody cover. Woody cover associated with fencerows, ditches, and woodlots adjacent to food sources and breeding habitat will likely improve non-breeding season survival, which is an influential vital rate in northern populations. © 2012 The Wildlife Society.     

Effects of Landscape Composition on Winter Survival of Northern Bobwhites

Abstract: In a manipulative experiment, we tested effects of select elements of landscape structure and composition on winter survival of northern bobwhites (Colinus virginianus) at Ames Plantation, Tennessee, USA. We hypothesized that abundance of closed canopy forested habitats (52% of the landscape) on Ames diminished usable space for bobwhite and provided usable space for a suite of important predators, thereby contributing to low winter survival. To test this hypothesis we divided a 2,217-ha portion of the property into 4 approximately equal areas. We altered landscape structure and composition by converting approximately 33% of the timber to early successional herbaceous plant communities on 2 treatment sites, which reduced percentage of landscape and edge density of closed canopy forest and increased percentage of landscape in early successional herbaceous communities, and left 2 control sites in their former composition. During one pretreatment year (1998–1999) and 3 posttreatment years (1999–2000, 2000–2001, 2001–2002), we estimated winter (15 Oct-10 Apr) survival on treatment and control sites from a radiomarked sample of 920 bobwhites. We used Cox Proportional Hazard models to test for effects of treatment (forest conversion) and covariates describing landscape structure and composition (% closed canopy forest, % early successional herbaceous, wooded edge density) on winter survival at multiple spatial scales. Winter survival on the treatment sites pooled across the 4 winter seasons was 41% compared to 32% for control sites. Additionally, for each 1 m/ha increase in closed canopy woods edge density within winter covey ranges, risk of mortality increased 0.3%. Our results suggest composition at the landscape scale and landscape structure at the local scale influence winter survival of bobwhite. Management strategies that alter composition and structure and increase usable space may be effective in mitigating winter mortality thereby altering population trajectories. Typical bobwhite management plans focus on improving quality of herbaceous vegetation structure within existing herbaceous patches, however, population processes may work at larger spatial scales influencing design and implementation of conservation programs.     

Relationships between brood size and parental provisioning performance in chinstrap penguins during the chick guard phase

 Chinstrap penguins (Pygoscelis antarctica) normally lay two eggs, but brood size is often reduced by mortality during incubation or after hatching. We hypothesized that this variation in brood size would affect the parents’ foraging behavior and their chick provisioning performance. We studied patterns of adult foraging trip duration and frequency, food load delivery, and chick growth rates in relation to brood size during the guard phase in four breeding seasons (1991–1994) on Seal Island, Antarctica. Within a given year, parents with two chicks made more frequent foraging trips to sea and may have transported larger food loads to the nest; however, the duration of foraging trips was unrelated to brood size. Overall, parents with two chicks spent ∼15% more time at sea than parents with only one chick. Both the frequency and duration of foraging trips varied between years. Foraging trip duration may partly reflect the birds’ foraging radius, which probably varies with time in response to shifts in krill distribution. Chick growth rate varied betwen years, but was related to brood size only in 1992, when chicks from two-chick broods grew significantly more slowly than chicks from one-chick broods. Food loads transported to chicks, as well as chick growth rates, were highest in 1994, when concurrent hydroacoustic studies indicated that regional krill biomass was severely depressed. This apparent anomaly suggests that the spatial scale of the krill survey may have been too coarse to detect some high-density krill aggregations within the penguins’ foraging range. Received: 26 September 1995 / Accepted: 12 May 1996     

Beneficial Insect Borders Provide Northern Bobwhite Brood Habitat

Strips of fallow vegetation along cropland borders are an effective strategy for providing brood habitat for declining populations of upland game birds (Order: Galliformes), including northern bobwhite (Colinus virginianus), but fallow borders lack nectar-producing vegetation needed to sustain many beneficial insect populations (e.g., crop pest predators, parasitoids, and pollinator species). Planted borders that contain mixes of prairie flowers and grasses are designed to harbor more diverse arthropod communities, but the relative value of these borders as brood habitat is unknown. We used groups of six human-imprinted northern bobwhite chicks as a bioassay for comparing four different border treatments (planted native grass and prairie flowers, planted prairie flowers only, fallow vegetation, or mowed vegetation) as northern bobwhite brood habitat from June-August 2009 and 2010. All field border treatments were established around nine organic crop fields. Groups of chicks were led through borders for 30-min foraging trials and immediately euthanized, and eaten arthropods in crops and gizzards were measured to calculate a foraging rate for each border treatment. We estimated arthropod prey availability within each border treatment using a modified blower-vac to sample arthropods at the vegetation strata where chicks foraged. Foraging rate did not differ among border treatments in 2009 or 2010. Total arthropod prey densities calculated from blower-vac samples did not differ among border treatments in 2009 or 2010. Our results showed plant communities established to attract beneficial insects should maximize the biodiversity potential of field border establishment by providing habitat for beneficial insects and young upland game birds.     

Home range and survival characteristics of male Bachman's Sparrows in an old-growth forest managed with breeding season burns

ABSTRACT.   Prescribed burning is essential for maintaining suitable habitat for Bachman's Sparrows ( Aimophila aestivalis ), but burns conducted during the breeding season may lead to site abandonment and low survival or productivity. We monitored a color-banded population of Bachman's Sparrow in Georgia for four breeding seasons to assess home range size, site fidelity, and survival in an area managed primarily using breeding season burns. Our study area was one of the last remaining tracts of old-growth longleaf pine ( Pinus palustris ), and alternating halves of the tract were burned during the breeding season during each year of our study. Mean home range size for males ( N = 46) during the breeding season was 3.1 ha based on 95% fixed kernel analysis and 1.8 ha based on minimum convex polygons. Breeding season burning had no effect on male site fidelity and home range characteristics. The proportion of males remaining on burned areas was similar to the proportion remaining on unburned areas. Shifts in home range centroids pre- and postburn were also similar for males on unburned (median = 49.7 m) and burned (median = 65.6 m) areas. In addition, the size of home ranges that were burned ( ha) was similar to that of home ranges that were not burned ( ha). Estimated annual survival for males was 0.59. The median shift in annual home range centers calculated for 38 males observed during multiple breeding seasons was 63 m and, coupled with our survival estimates, suggest greater site fidelity than previously reported. These results suggest that breeding season burns were not as detrimental to Bachman's Sparrows as reported at other locations, and such burns may be helpful in maintaining suitable habitat.     

Space use of the Siberian flying squirrel Ptevomys volans in fragmented forest landscapes

We studied the space use of the Siberian flying squirrel in fragmented forest landscapes in southern Finland in 1996- 1999. Twenty-four adult males and 23 adult females were radio trucked in three different study areas. The use of different landscape elements by flying squirrels was compared to their availability using compositional analysis. Effects of fragmentation on flying squirrels were studied by comparing the use of different habitat types, number of used patches, and size of home range to the principal components formed from the landscape variables patch size, patch isolation, area of spruce-dominated forests, and area of other habitats with trees.
Flying squirrels preferred spruce- and deciduous-dominated forests, but other habitats with trees were also used for moving and foraging. These less preferred habitats connected spruce and deciduous forest patches in a matrix of open areas. Males used several separate patches of preferred habitat, but females usually stayed in one patch. The spacing behaviour of males was affected by the structure of the landscape in a way that home ranges were larger and males used more spruce patches in the more highly fragmented landscape. Home-range size of females was not affected by the landscape structure. Basically, the space use of males seemed lo be reflected by the location and number of female home ranges. In the study area where female density was high, the home ranges of males were small. Our results give empirical evidence of the effects of habitat loss and landscape connectivity for the Siberian flying squirrel and the implications of these for the conservation of the species.     

Nestling immunocompetence and testosterone covary with brood size in a songbird

The social and ecological conditions that individuals experience during early development have marked effects on their developmental trajectory. In songbirds, brood size is a key environmental factor affecting development, and experimental increases in brood size have been shown to have negative effects on growth, condition and fitness. Possible causes of decreased growth in chicks from enlarged broods are nutritional stress, crowding and increased social competition, i.e. environmental factors known to affect adult steroid levels (especially of testosterone and corticosteroids) in mammals and birds. Little, however, is known about environmental effects on steroid synthesis in nestlings. We addressed this question by following the development of zebra finch (Taeniopygia guttata) chicks that were cross-fostered and raised in different brood sizes. In line with previous findings, nestling growth and cell-mediated immunocompetence were negatively affected by brood size. Moreover, nestling testosterone levels covaried with treatment: plasma testosterone increased with experimental brood size. This result provides experimental evidence that levels of circulating testosterone in nestlings can be influenced by their physiological response to environmental conditions.     

Effects of Understory Vegetation Management on Brood Habitat for Northern Bobwhites

Abstract: Northern bobwhite (Colinus virginianus) populations have experienced severe declines for several decades, and declines have been particularly precipitous in the southern United States. These declines are partially attributable to large-scale conversions of potential habitat to short-rotation pine (Pinus spp.) forests managed for wood fiber production and fire exclusion in pine-dominated landscapes. We used standard arthropod sampling techniques, human-imprinted bobwhite chicks, and vegetation response to evaluate effects of different understory vegetation management practices on brood habitat quality within a commercially managed pine forest in Louisiana, USA, during 2002–2005. Specifically, we evaluated effects of mowing, prescribed fire during the growing season, prescribed fire in combination with imazapyr application, and no vegetation management on arthropod abundance and diversity, vegetation response, and the probability of bobwhite chicks successfully capturing an arthropod. Bobwhite chicks were more successful at capturing arthropods, and arthropod abundance and diversity were greatest, in plant communities managed using prescribed fire and imazapyr. Forest stands managed using a combination of fire and imazapyr were managed primarily to benefit the federally endangered red-cockaded woodpecker (Picoides borealis; RCW). Our findings suggest that management directed toward improving forest condition for RCWs improves habitat quality for brooding bobwhites. However, bobwhite chicks in our study area were less successful at capturing arthropods than were chicks in other studies in the southeastern United States. Brood-rearing habitat in pine forests similar to those we studied may be of generally poor quality, and could be related to precipitous declines of bobwhites in the West Gulf Coastal Plain. Managers should recognize that creating high-quality brood habitat in forests similar to those we studied will require more intensive management of understory vegetation than we studied.     

Using Human-Imprinted Chicks to Evaluate the Importance of Forbs to Sage-Grouse

Abstract Although several studies have indicated the importance of forbs in brood habitats, no studies have quantified direct effects of the amount of forb cover on sage-grouse (Centrocercus urophasianus) chicks. In 2002 and 2003, we conducted field experiments in Middle Park and Moffat County, Colorado, USA, respectively. Our objective was to quantify effects of 3 levels of forb cover in brood habitat on mass gain and feather growth of human-imprinted sage-grouse chicks. The results indicate that increasing forb cover in brood areas with <20% forb cover may lead to increased chick survival and grouse productivity.     

How landscape scale changes affect ecological processes in conservation areas: external factors influence land use by zebra (Equus burchelli) in the Okavango Delta

Most large‐bodied wildlife populations in sub‐Saharan Africa only survive in conservation areas, but are continuing to decline because external changes influence ecological processes within reserves, leading to a lack of functionality. However, failure to understand how landscape scale changes influence ecological processes limits our ability to manage protected areas. We used GPS movement data to calculate dry season home ranges for 14 zebra mares in the Okavango Delta and investigated the effects of a range of landscape characteristics (number of habitat patches, mean patch shape, mean index of juxtaposition, and interspersion) on home range size. Resource utilization functions (RUF) were calculated to investigate how specific landscape characteristics affected space use. Space use by all zebra was clustered. In the wetter (Central) parts of the Delta home range size was negatively correlated with the density of habitat patches, more complex patch shapes, low juxtaposition of habitats and an increased availability of floodplain and grassland habitats. In the drier (Peripheral) parts of the Delta, higher use by zebra was also associated with a greater availability of floodplain and grassland habitats, but a lower density of patches and simpler patch shapes. The most important landscape characteristic was not consistent between zebra within the same area of the Delta, suggesting that no single foraging strategy is substantially superior to others, and so animals using different foraging strategies may all thrive. The distribution and complexity of habitat patches are crucial in determining space use by zebra. The extent and duration of seasonal flooding is the principal process affecting habitat patch characteristics in the Okavango Delta, particularly the availability of floodplains, which are the habitat at greatest risk from climate change and anthropogenic disturbance to the Okavango's catchment basin. Understanding how the factors that determine habitat complexity may change in the future is critical to the conservation of large mammal populations. Our study shows the importance of maintaining flood levels in the Okavango Delta and how the loss of seasonal floodplains will be compounded by changes in habitat configuration, forcing zebra to change their relative space use and enlarge home ranges, leading to increased competition for key resources and population declines.     

Northern bobwhite breeding season habitat selection in fire-maintained pine woodland

Despite the acknowledged importance of prescribed fire in creating northern bobwhite (Colinus virginianus) breeding cover, little research has investigated bobwhite breeding season habitat selection relative to time since fire. In 2016 and 2017, we monitored radio-tagged bobwhite on a 17,000-ha portion of a military installation managed with frequent (every ~3 years) prescribed fires, applied during the growing and dormant seasons. We monitored bobwhite to determine which vegetation characteristics associated with prescribed burning were important to bobwhite breeding season habitat selection at the microsite (i.e., telemetry location compared to nearby random location) and the macrosite scale (i.e., the burn-unit containing the location compared to study area availability). During 2 breeding seasons, we collected 2,315 bobwhite locations and compared percent cover of vegetation, days since burn, basal area, and distance to key landscape features (e.g., stream, wildlife opening) at a subset of microsite locations (301 locations during 2016 and 890 locations during 2017) to paired random locations. At the microsite scale, bobwhite selected lower basal area of hardwoods, greater woody understory cover, greater other (not wiregrass [Aristida stricta]) grass cover, and greater forb cover than at random points. At the macrosite scale, bobwhite selected units with <4.6 m²/ha basal area (combined hardwoods and pines) in 2016 and units with <9.2 m²/ha basal area in 2017. At the macrosite scale, bobwhite selected for areas burned in the dormant season of the same year, avoided areas burned in the growing season of the same year, and used other times since last burn categories proportionate to their availability. The selection for a low basal area at both scales indicates prescribed fire effects would be limited by shading from dense overstory, and the shrubs, grasses, and forbs that provide essential cover for bobwhite during the breeding season will not develop. In lower productivity soil regions similar to our study area, we advise that thinning operations set target basal areas below 10 m²/ha to create and maintain breeding season habitat for northern bobwhite. © 2019 The Wildlife Society     

Parental and chick responses of Laughing Gulls (Leucophaeus atricilla) to increase of flight costs and brood size

One main line of thought in life history theory is that investment in offspring must be balanced to minimize negative impacts on adult survival and future breeding. Seabirds have been regarded as fixed investors, although they exhibit a whole gradient of life history traits. We studied the consequences of brood size (one and three chicks) and of increased flight costs to one mate of a pair (3- and 5-cm trimming of the edge of the primary feathers) on parental response and on survival and body condition of chicks of Laughing Gulls (Leucophaeus atricilla). Parent gulls modified their nest attendance when their mate was handicapped, in a pattern dependent on the sex of the latter. Trimming of males affected chicks more severely than that of females. On its part, brood size affected amount of feeding sessions. Both chick body condition and survival were negatively affected by larger broods and by increased flight costs of one of their parents, especially when it was the male. Overall, parental inversion exhibited adjustments depending on the requirements of the brood and the fact that males compensated better the increased flying costs of their mates than vice versa. Despite a certain capacity by the males to compensate for the increased flight costs of the females, compensation was insufficient, and much less so in females, especially in larger broods, affecting chicks’ body condition and survival.     

Influence of conservation reserve program mid-contract management and landscape composition on northern bobwhite in tall fescue monocultures

The United States Department of Agriculture (USDA) authorized mid-contract management (MCM) in 2004 to restore and maintain plant species composition and structural diversity in aging Conservation Reserve Program (CRP) fields for the northern bobwhite (Colinus virginianus) and other grassland-dependent wildlife. We implemented 3 USDA-approved MCM regimes (i.e., strip disking, strip glyphosate spraying, and strip glyphosate spraying in combination with legume interseeding) in 60 tall fescue (Festuca arundinaceae) CRP monocultures in south-central Illinois, USA, during 2005–2008. We hypothesized that adult bobwhite relative densities and brood presence would increase following MCM that effectively restored early successional plant communities in otherwise monotypic stands of tall fescue. We estimated annual adult bobwhite relative densities and brood presence-absence in managed and unmanaged CRP. We modeled vegetation characteristics and landscape composition to identify factors influencing adult densities and brood presence. Adult relative densities were 2-fold greater in managed fields than in unmanaged fields, and were negatively correlated with greater percentages of grass cover. Adult densities were positively correlated with greater plant species diversity, and greater percentages of bare ground and legume cover. Logistic regression and odds ratio estimates indicated that fields managed with glyphosate-interseed and glyphosate treatments were 39.6% more likely to have broods than unmanaged CRP, whereas disked fields were 10.0% more likely than unmanaged CRP. These models indicated that the probability of brood presence was greater in fields with increased percentage of bare ground, greater plant species diversity, and decreased percentage of grass and litter cover. These findings suggest that a 3-year rotation of glyphosate or glyphosate-interseed treatments can enhance habitat conditions for adult bobwhites and broods in CRP tall fescue monocultures. © 2011 The Wildlife Society.     

The importance of post‐fire regrowth for sable antelope in a Southern African savanna

Burning is commonly used in savannas to stimulate grass regrowth for grazing ungulates. We recorded the relative use of burns occurring at different stages in the seasonal cycle, as well as in different regions of the landscape by two herds of sable. We also recorded behavioural measures of foraging efficiency and faecal nutrient contents as an indication of nutrient gains. Sable consistently concentrated their grazing on burned areas provided there was sufficient green regrowth during the dry season. In these circumstances they grazed for longer per feeding station, showed a slower step rate while foraging, and shorter between‐patch moves, and a higher probability of encountering acceptable food per step taken while foraging than on unburnt areas. In the year when only a burn with insufficient regrowth was available, sable continued to forage in the area that had been burned during the previous year. Faecal crude protein was substantially higher at the end of the dry season in the year when burned areas were utilized. Accordingly early dry season fires can be important in helping sable bridge the nutritional limitations posed by the dry season, provided sufficient soil moisture remains to promote adequate grass regrowth.     

Behavioral modifications lead to disparate demographic consequences in two sympatric species

Life‐history theory suggests species that typically have a large number of offspring and high adult mortality may make decisions that benefit offspring survival in exchange for increased adult risks. Such behavioral adaptations are essential to understanding how demographic performance is linked to habitat selection during this important life‐history stage. Though studies have illustrated negative fitness consequences to attendant adults or potential fitness benefits to associated offspring because of adaptive habitat selection during brood rearing, equivocal relationships could arise if both aspects of this reproductive trade‐off are not assessed simultaneously. To better understand how adaptive habitat selection during brood rearing influences demographics, we studied the brood survival, attendant parental survival, and space use of two sympatric ground‐nesting bird species, the northern bobwhite (hereafter: “bobwhite”; Colinus virgininanus) and scaled quail (Callipepla squamata). During the 2013–2014 breeding seasons, we estimated habitat suitability across two grains (2 m and 30 m) for both species and determined how adult space use of these areas influenced individual chick survival and parental risk. We found the proportion of a brood's home range containing highly suitable areas significantly increased bobwhite chick survival (β = 0.02, SE = 0.006). Additionally, adult weekly survival for bobwhite was greater for individuals not actively brooding offspring (0.9716, SE = 0.0054) as compared to brooding adults (0.8928, SE = 0.0006). Conversely, brood habitat suitability did not influence scaled quail chick survival during our study, nor did we detect a survival cost for adults that were actively brooding offspring. Our research illustrates the importance of understanding life‐history strategies and how they might influence relationships between adaptive habitat selection and demographic parameters.     

Responses to land cover and grassland management vary across life‐history stages for a grassland specialist

Grassland birds have exhibited dramatic and widespread declines since the mid‐20th century. Greater prairie chickens (Tympanuchus cupido pinnatus) are considered an umbrella species for grassland conservation and are frequent targets of management, but their responses to land use and management can be quite variable. We used data collected during 2007–2009 and 2014–2015 to investigate effects of land use and grassland management practices on habitat selection and survival rates of greater prairie chickens in central Wisconsin, USA. We examined habitat, nest‐site, and brood‐rearing site selection by hens and modeled effects of land cover and management on survival rates of hens, nests, and broods. Prairie chickens consistently selected grassland over other cover types, but selection or avoidance of management practices varied among life‐history stages. Hen, nest, and brood survival rates were influenced by different land cover types and management practices. At the landscape scale, hens selected areas where brush and trees had been removed during the previous year, which increased hen survival. Hens selected nest sites in hay fields and brood‐rearing sites in burned areas, but prescribed fire had a negative influence on hen survival. Brood survival rates were positively associated with grazing and were highest when home ranges contained ≈15%–20% shrub/tree cover. The effects of landscape composition on nest survival were ambiguous. Collectively, our results highlight the importance of evaluating responses to management efforts across a range of life‐history stages and suggest that a variety of management practices are likely necessary to provide structurally heterogeneous, high‐quality habitat for greater prairie chickens. Brush and tree removal, grazing, hay cultivation, and prescribed fire may be especially beneficial for prairie chickens in central Wisconsin, but trade‐offs among life‐history stages and the timing of management practices must be considered carefully.     

Responses by Central‐Place Foragers to Manipulations of Brood Size: Parent Flickers Respond to Proximate Cues but do not Increase Work Rate

Manipulations of brood size measure the willingness or ability of parents to invest in offspring and different reproductive roles may lead to differences in feeding effort between the sexes. Parental investment in birds is usually assessed by quantifying feeding rates, but this provides an incomplete picture of parental effort because it fails to account for how parents collect food on the landscape. We studied northern flickers (Colaptes auratus), a woodpecker in which males provide the majority of parental care and used a repeated measures design and short‐term (24 h) brood enlargements (N = 35) and reductions (N = 27) to assess effects of treatment on feeding rates to nestlings and parental foraging behaviour. Parents of enlarged broods did not significantly increase feeding rate, resulting in a decline in nestling mass. Parents of reduced broods decreased their feeding rates by 84%, but increased per capita feeding rates, resulting in nestling mass gain. The variation in feeding rates to enlarged broods was not influenced by feather corticosterone, body condition, feather re‐growth rate or mass change between the incubation and nestling periods. Foraging pattern on the landscape remained the same during the enlarged treatment for both sexes. We conclude that flickers respond to proximate cues in brood demands, but do not increase feeding rates to enlarged broods, at least in the short term. A literature review suggested that this lack of response is atypical for short‐lived species. We hypothesize that parents in species with large home ranges and long nestling periods face energetic limitations that constrain their ability to respond to enlarged broods. We encourage future studies to assess foraging behaviour on the landscape to document important trade‐offs for parents such as predation risk and energy expenditure while feeding offspring.     

Foraging range of king penguins Aptenodytes patagonicm during summer at Marion Island

Foraging ranges of king penguins Aptenodytes patagonicus were estimated by combining information on the feeding rates to chicks and brood shift lengths of adults (assessed by daily weighings of large chicks and daily checks of marked birds brooding small chicks) with measurements of travelling speeds and activity budgets at sea (assessed using remote recording devices). Adults brooding small chicks were relieved on average every 13 days and large chicks were fed every four days. Adults with large chicks spent 36% of their time, between attachment of the device and recapture, travelling at an average speed of 8.7 km.h^-1. This gives an estimated mean maximum foraging range of about 300 km. Adults attending small chicks spent 19% of their time away swimming, giving an estimated mean maximum foraging range of 225 km. Extreme foraging ranges for all birds were 75 and 902 km for penguins returning between two and 24 days at sea, respectively. Total distance travelled was highly correlated with time away from the colony.     

Home range and habitat selection of spotted owls in the central Sierra Nevada

We studied home range and habitat selection of radio-marked adult California spotted owls (Strix occidentalis occidentalis) randomly selected from among the breeding population of owls in the central Sierra Nevada, California from June to October 2006. The most parsimonious home-range estimate for our data was 555 ha (SE = 100 ha). Home-range size was positively correlated with the number of vegetation patches in the home range (habitat heterogeneity). We used resource selection ratios to examine selection of vegetation types by owls within our study area. Owl home ranges contained a high proportion of mature conifer forest, relative to its availability, although the confidence interval for this estimate overlapped one. We also used resource selection functions (RSF) to examine owl foraging habitat selection. Relative probability of selection of foraging habitat was correlated with vegetation classes, patch size, and their interaction. Owls showed highest selection rates for large patches (>10 ha) of pole-sized coniferous forest. Our results suggested that spotted owls in the central Sierra Nevada used habitat that contained a high proportion of mature conifer forest at the home-range scale, but at a finer scale (foraging site selection) owls used other vegetation classes interspersed among mature forest patches, consistent with our hypothesis that spotted owls may use other forest types besides old growth and mature forests when foraging. Our study provides an unbiased estimate of habitat use by spotted owls in the central Sierra Nevada. Our results suggest that forest managers continue to protect remaining mature and old-growth forests in the central Sierra Nevada because owl home ranges contain high proportions of these habitats. However, our results also showed that owls used younger stands as foraging habitat so that landscape heterogeneity, with respect to cover types, may be an important consideration for management but we did not attempt to relate our findings to fitness of owls. Thus management for some level of landscape heterogeneity for the benefit of owls should proceed with caution or under an adaptive management framework. © 2011 The Wildlife Society.