The Cerulean Warbler (Dendroica cerulea) tops many lists of species of conservation concern because of severe population declines and habitat loss. Here we present the first robust estimates of annual survival and population growth rates for this species. We used capture—mark—recapture models to estimate survival of adult male Cerulean Warblers in an eastern Ontario population that has been studied since 1994. Adult male survival probability (ϕ) was constant over time in our best-supported model. Our second-best-supported model indicated a negative effect of a 1998 ice storm on survival. The third-best-supported model indicated a significant year effect on survival. On the basis of those results and previously published estimates of annual fecundity, we calculated a population growth rate using a two-stage Leslie matrix. Population growth rate (λ) was 0.73, using the estimate for constant survival. Model elasticities imply that adult mortality had a stronger effect on λ than did seasonal fecundity. Oversummer survival estimates suggest that events during migration or on wintering grounds are responsible for most adult male mortality. It appears that our study population, thought to be one of the healthiest known for this species, may not be currently reproducing at a high enough rate to accommodate adult mortality. However, caution must be used when interpreting those results, given the possibility of underestimating survival and fecundity of this species.

The group of small forest robins, or akalats, that dwell in lowland and montane forests in Africa have complicated parapatric or partly overlapping distributions, the details of which are still being discovered. Here, we use external morphology and mitochondrial and nuclear DNA sequence data to determine the reciprocal monophyly of several populations, including one form that is related to Sheppardia lowei and S. montana. Those data corroborate the recognition of a new species, Sheppardia aurantiithorax, and show relatively high levels of sequence divergence among populations of the different species. The discovery of this new species, narrowly endemic in the Eastern Arc montane forests, emphasizes the complex biodiversity of the region and underscores the need for prompt and effective conservation measures.

Previous reports have stated that Tufted Puffins (Fratercula cirrhata) lose all of their flight feathers simultaneously (or nearly so) during flight-feather molt and replace them in no apparent order. In contrast, we found that captive second-year (SY) Tufted Puffins (1) typically require 15 and 10 days to lose their primaries and secondaries, respectively, during their first flight-feather molt, and an average of 21 days to lose all of their remiges; and (2) replace their primaries in either of two discrete sequences. In 9 of 13 birds, primary molt began at the innermost primary, P1, and progressed distally to the outermost functional primary, P10. However, in the remaining four birds, primary molt began in the middle of the primaries (P5-P7) and progressed both distally to P10 and proximally toward P1. Before the proximal wave reached P1, a second wave of molt was initiated at P1 and progressed distally, typically replacing P2 and P3 before reaching the proximal wave. Such polymorphism in flight-feather molt sequence is rare in birds, having been reported previously only in a few passerine species. Secondary molt began about 13 days after onset of primary molt and finished at about the same time as primary molt, resulting in a total duration of flight-feather molt of ∼54 days and a flightless period of ∼40 days.

We conducted winter censuses of two short-distance migrants, Hermit Thrushes (Catharus guttatus) and Yellow-rumped Warblers (Dendroica coronata), over seven years in five different habitats to determine whether their local abundances could be predicted by fruit pulp biomass. Sampled habitats were stands of upland and bottomland hardwood, loblolly pine (Pinus taeda), longleaf pine (P. palustris), and young (<10 years) longleaf pine. Hermit Thrush abundance, which was highest in bottomland hardwood habitats, was positively related to total dry mass of fruit pulp. Those results are consistent with the hypothesis that resource availability affects the local distribution of migrant passerines on their wintering grounds. Our results also indicate that bottomland hardwood habitats in the southeastern United States may be especially important to wintering Hermit Thrushes. Yellow-rumped Warbler abundance was correlated with ripe-fruit pulp dry mass of Myrica cerifera, a major source of winter food for that species. However, because M. cerifera pulp dry mass was confounded with habitat type, we could not distinguish the relative importance of fruit resources and habitat for Yellowrumped Warblers. Our results underscore the importance of fruit to wintering birds. However, the overall percentage of variation in winter bird abundance explained by differences in ripefruit biomass was modest, indicating that other factors are also important.

Data on spacing behavior of the Eurasian Three-toed Woodpecker (Picoides tridactylus) are rare, and systematic observations are lacking. I used homing technique (>90%) and triangulation to document range use of 28 radiotagged birds in an alpine mountain forest in southeastern Germany between 1994 and 2000. Common home range of a pair (x ± SE, n = 10) identified by the adaptive kernel method (95% use distribution) during the nesting period averaged 86.4 ± 23.4 ha and varied a great deal between pairs (range 33.9–287.4 ha). Although ranges of females (69.4 ± 15.4 ha, n = 14) appeared larger than those of males (45.7 ± 10.3 ha, n = 10), the difference was not significant. Prior to nesting and during the postnesting period, both sexes used seemingly larger home ranges than during nesting (≤381.7 ha); but again, the difference was not significant. Home ranges of mates (n = 20) during the nesting period overlapped an average of 66.5 ± 5.7% (≤100.0%); female ranges and core areas overlapped male ranges to a significantly greater extent than male ranges overlapped those of females. Nearly all home ranges bordered or overlapped those of their neighbors. Ranges of neighboring male-female combinations (n = 11) overlapped by 17.6 ± 3.9% during the nesting period, with an increasing tendency to overlap toward the end of the breeding season. Because areas used by Eurasian Three-toed Woodpeckers remained stable over the breeding season, I propose consideration of home ranges during nesting as a reliable estimate of species area requirements for use in management plans.

In geese, growth regulates survival in the first year. We examined whether early growth, which is primarily governed by environmental conditions, also affects the probability that individuals that survive their first year enter the breeding population. We used logistic regression on a sample of Black Brant (Branta bernicla nigricans) that were weighed at a known age in their first summer and observed during winter (indicating that they had survived the principal mortality period in their first year) to study whether early growth influenced the probability that those individuals would be recruited into the breeding population. We also examined the effects of cohort (1986–1996), sex, age when measured, and area where individuals were reared. The model with the lowest Akaike's Information Criterion score contained body mass, age (days) at measurement, cohort, sex, and brood-rearing area. Models that included variable mass had 85% of the cumulative model weight of the models we considered, indicating that gosling mass had a substantial effect on probability of them entering the breeding population. Females were more likely to be detected breeding than males, which is consistent with the differential fidelity of the sexes. Of individuals that survived the first year, larger goslings were more likely to become breeders. More recent cohorts were less likely to have been detected as breeders. Our findings indicate that environment during the growth period affects the ability of individuals to enter the breeding population, even after accounting for the effects of growth on survival.

Food availability during winter may determine habitat use and limit populations of overwintering birds, yet its importance is difficult to judge because few studies have experimentally tested the response of nonbreeding birds to changes in resource abundance. We experimentally examined the link between fruit availability and habitat use by manipulating winter abundance of Myrica cerifera L. (Myricaceae) fruits in managed longleaf (Pinus palustris) and loblolly (P. taeda) pine stands in South Carolina. Myrica cerifera is a common understory shrub in the southeastern United States and provides lipid-rich fruit in late winter (February and March), when insects and other fruits are scarce. On treatment plots, we covered fruiting M. cerifera shrubs with netting in early winter to prevent birds from eating their fruits. In late February, when M. cerifera fruit crops were largely depleted elsewhere on our study site, we uncovered the shrubs and documented the response of the bird community to those patches of high fruit availability. Relative to control plots, total bird abundance (excluding the most common species, Yellow-rumped Warbler [Dendroica coronata]) and species richness did not change after net removal. Yellow-rumped Warblers, however, became significantly more abundant on treatment plots after net removal, which suggests that they track M. cerifera fruit abundance. We suggest that M. cerifera plays a role in determining the local distribution of wintering Yellow-rumped Warblers at our study site. To put these results into a management context, we also examined the effect of prescribed fire frequencies on M. cerifera fruit production. Across pine stands with different fire regimes, M. cerifera fruit abundance increased with the number of years since burning. It takes 4–6 years for individuals to recover sufficiently from a burn to produce large quantities of fruit. Thus, shorter intervals between burns will reduce winter fruit availability. Taken together, these results suggest that within those pine plantations, the local winter distribution of at least one common migratory bird is closely tied to fruit abundance, which in turn is tied to the frequency of prescribed fires.

I analyzed the species composition, structure, and trophic organization of bird assemblages in the forest canopy around Manaus, Brazil. Using three canopy towers located in primary terra firme forests, I conducted 117 censuses over a 13 month period, recording 160 bird species. The three study sites had similar species richness (between 126 and 128 species), sharing 95 species in common, which accounted for >90% of all individual records. Most species recorded in the canopy (110) belonged to the core canopy avifauna. The other 50 species included migrants (13), species that feed overhead (8), species from lower strata (15), night birds (3), and vagrants or visitors from open areas and second-growth forests (11). Most of those species, however, appeared in very low numbers in the forest canopy, except understory frugivores, which regularly fed on canopy fruits. Among the migratory species were some Nearctic (6), Austral (3), and species probably holding both migratory and resident populations in the area (4). Additionally, I found evidence that two species of parrots perform seasonal movements, leaving the forest canopy around Manaus during the dry season. Frugivores dominated the canopy avifauna in abundance, but contradicting results reported from other Neotropical forest canopies, insectivores and frugivores had equal species richness. The canopy avifauna was highly homogeneous among sites in terms of species richness, distribution among abundance classes, and number of species in each feeding guild, habitat, and microhabitat. As in Costa Rica, the canopy avifauna of Manaus was mostly composed by typical canopy bird species, and not by edge-living species as reported from Panama. I suggest that habitat fragmentation may affect the bird community composition in the forest canopy, allowing a higher influx of opportunistic species.

We studied rapid yolk deposition (RYD) in Barn Owls (Tyto alba) on the basis of the analysis of 26 eggs laid by “dye-dosed” captive female Barn Owls in five different broods. Pictures of yolks were examined to assess daily rates of yolk deposition. We used those data in combination with data from the dissection of ovaries of another five breeding females. We found that the total duration between initiation of RYD and laying of the corresponding egg was only 13.6 days, with an interval between yolk completion and oviposition of 2.4 days. The total number of follicles that may have given eggs was found to be 25. That high number of follicles and the short RYD period explain the particularly high reproductive potential of this nocturnal raptor species.

Seasonal patterns of singing activity of male birds have been thoroughly studied, but little is known about how those patterns vary with time of day. Here, we censused mated and unmated male Nightingales (Luscinia megarhynchos) at four different hours of the day throughout the breeding cycle. In unmated males, singing activity increased until the young hatched in their neighborhood, and the seasonal variation was similar at each of the four hours of the day. In mated males, however, the seasonal patterns of singing activity differed between hours of the day. In morning (about the hour of egg-laying) and during the dusk chorus, the singing activity of mated males was strongly influenced by the females' reproductive state: singing activity was low before egg-laying and during incubation, but high during the egg-laying period. In the dawn chorus, however, singing activity showed a similar seasonal pattern in mated and unmated males and was high until late stages of the breeding cycle. Our results suggest that the social context influences singing behavior to a varying degree across the season, and that this variation also depends on time of day. The hour of data collection thus is an important but often neglected factor when seasonal changes of singing activity are studied.

During the seven-year period from 1995 to 2001, we conducted a detailed, demographic study of a population of Western Bluebirds (Sialia mexicana) in Oregon. Using a data set consisting of individual capture histories for ≈8,000 birds, we estimated age-specific and study-year specific survival estimates of adult males and females. High juvenile recruitment enabled us to generate accurate estimates of juvenile survival from fledging to first breeding attempt. We analyzed fecundity patterns, including nesting phenology, clutch success, and overall reproductive success for nearly 1,200 nesting attempts. Temporal variation in survival and fecundity had strong demographic consequences. Asymptotic population growth analysis suggested a slowly growing population. However, variation in vital rates led to population declines even over the relative short timescale of our study, making the conservation status of this species uncertain. In addition to those results, we discuss the costs and benefits of using data collected by volunteers to study demographic processes.

Estimation of daily survival probabilities of nests is common in studies of avian populations. Since the introduction of Mayfield's (1961, 1975) estimator, numerous models have been developed to relax Mayfield's assumptions and account for biologically important sources of variation. Stanley (2000) presented a model for estimating stage-specific (e.g. incubation stage, nestling stage) daily survival probabilities of nests that conditions on “nest type” and requires that nests be aged when they are found. Because aging nests typically requires handling the eggs, there may be situations where nests can not or should not be aged and the Stanley (2000) model will be inapplicable. Here, I present a model for estimating stage-specific daily survival probabilities that conditions on nest stage for active nests, thereby obviating the need to age nests when they are found. Specifically, I derive the maximumlikelihood function for the model, evaluate the model's performance using Monte Carlo simulations, and provide software for estimating parameters (along with an example). For sample sizes as low as 50 nests, bias was small and confidence interval coverage was close to the nominal rate, especially when a reduced-parameter model was used for estimation.

Like most other penguin species, Magellanic Penguins (Spheniscus magellanicus) are large-bodied birds that incubate their eggs for a prolonged period on hard substrates with little nesting material—all circumstances that could lead to high rates of egg breakage. However, Magellanic Penguin eggs at Punta Tombo, Argentina are seldom broken. From 1984 to 2001, only 2.6% of 10,023 eggs in our study areas broke or cracked. Most of those were broken in unusual or catastrophic events, mainly penguin fights and rainstorms. Low breakage rates appear to be attributable to thick eggshells. Shells of Magellanic Penguin eggs averaged 0.81 mm without the egg membranes—at least 56% thicker than expected for bird eggs of similar mass. The calcium required for those thick eggshells cannot be supplied by normal food intake because females lay eggs during a fasting period. It is also unlikely that sufficient skeletal calcium can be mobilized. An alternative potential calcium source is mollusk shells. To determine whether female penguins were selectively ingesting calcium to form thick eggshells, we examined stomach contents of birds during the egg period (settlement, egg laying, and early incubation) and the post-egg period (late incubation and chick rearing). Both females and males were more likely to have mollusk shells in their stomachs during the egg period than during the post-egg period. However, females were much more likely than males to have shells in their stomachs during the egg period, whereas the proportions of males and females with mollusk shells did not differ in the post-egg period. Selective ingestion of mollusk shells by Magellanic Penguins, resulting in thick eggshells, appears to be an adaptive response that reduces egg breakage.

Hybrid male Vidua were observed in the field and recorded to document host song mimicry. The mtDNA of one male was sequenced to identify the maternal parent. The hybrid males mimicked songs of Melba Finch (Pytilia melba), the usual host of Long-tailed Paradise Whydah (V. paradisaea), but the mtDNA matched that of indigobirds (V. chalybeata or another species), which parasitize and mimic other estrildid finches. This combination of song behavior and genetics is consistent with a two-generation history that began with a female indigobird (e.g. V. chalybeata) laying in a Melba Finch nest rather than in a nest of her usual host (e.g. Red-billed Firefinch [Lagonosticta senegala]). Her daughter, genetically an indigobird, imprinted on her Melba Finch foster parents and then mated with a male paradise whydah mimicking Melba Finch song. She also laid eggs in Melba Finch nests. Her son, the male hybrid carrying his grandmother's indigobird mtDNA, learned and later mimicked Melba Finch song. Genetic identification of the maternal species origin of this hybrid supports a model of mate choice based on mimetic song in the Vidua finches.

High nest-predation risk is often associated with forest edges. Most nest predators in boreal coniferous forests of North America are forest specialists living in mature stands. Nest predators have been studied mainly through use of artificial nests; knowledge of their behavior remains limited. We used radiotelemetry to examine movement patterns, relative to forest edge, of a forest nest predator, the Gray Jay (Perisoreus canadensis), in boreal coniferous forest. Each of 11 family groups of Gray Jays monitored in early summer exhibited a marked association with forest edges. Jays were found within 30 m of the forest edges more often than expected from random use of mature forest. Furthermore, jays traveled more slowly near forest edges than in the forest interior. Because forest edges apparently represent prime foraging habitat for Gray Jays, narrow forest strips left by logging could act as ecological traps for mature-stand songbirds before stands regenerate in adjacent clearcuts.

Avian studies are often interpreted using dual (e.g. ¹³C, ¹⁵N) isotope models, assuming turnover of both isotopes occur at similar rates, but only a few studies have quantified turnover rates for more than one of those isotopes simultaneously. To test the generality of previous turnover and fractionation estimates and assumption of synchronous C and N patterns of turnover rates, we captured Dunlin (Calidris alpina pacifica) wintering in the Fraser River Delta, British Columbia, and derived isotopic turnover rates and diet-tissue fractionation factors by experimentally manipulating diet. Birds (n = 15) were initially fed a terrestrially derived diet (mean δ¹³C: −24.7‰, mean δ¹⁵N: 3.5‰) for 54 days. A treatment group (n = 11) was then switched to a marine-derived diet (mean δ¹³C: −18.3‰, mean δ¹⁵N: 13.7‰); a control group (n = 4) was maintained on the terrestrial diet for a further 59 days. An exponential model described patterns of isotopic turnover for ¹³C and ¹⁵N, and turnover rates and half-lives of the two isotopes were correlated, confirming the assumption of synchronous patterns of turnover for those isotopes. The half-lives for ¹³C and ¹⁵N in Dunlin whole blood were 11.2 ± 0.8 days and 10.0 ± 0.6 days, respectively, and are among the lowest values obtained to date for wild birds. Variation in turnover rate among individuals was not related to indices of body condition.

Adult male Green Woodhoopoes (Phoeniculus purpureus) are only 5–8% larger than adult females in most linear measures but have 36% longer bills. Such sexual dimorphism may result from sexual selection, reproductive role division, or ecological separation. Here, we show that there is little evidence that sexual selection is currently acting on bill dimorphism in the Green Woodhoopoe. (1) Breeding males did not have longer bills than nonbreeding males. (2) There was no significant relationship between bill length and reproductive success of breeding males. (3) Although there was greater variation in male than in female bill length, the coefficient of variation (5.3%) fell within the range of those for naturally selected traits. (4) Although male bill length was found to be positively allometric with body mass, female bill length followed a similar relationship and there was no significant difference between the allometric slopes of the two sexes. Maintenance of the bill dimorphism by reproductive role division also seems unlikely when considering the nesting and provisioning characteristics of the species. We therefore conclude that the extreme sexual dimorphism in Green Woodhoopoe bill length is maintained by ecological separation to reduce foraging competition. We cannot, however, rule out the possibility that the sexual dimorphism initially evolved as a consequence of sexual selection.

Studies of the dawn chorus in birds have focused mainly on the behavior and song output of males and on the function(s) of male song. Less attention has been paid to the females' behavior and to communication between members of a pair. In Great Tits (Parus major), males sing vigorously at dawn in the vicinity of the female's nest hole just before and during egg laying. We studied the female's vocal behavior during the dawn chorus as well as communication between pair members. All females vocally interacted with their mates from inside the nest box. Females produced a sound with a very low sound-pressure level only audible from few meters, which we have named the “quiet call.” This quiet call was unique to females and was only produced from inside the nest box. To our knowledge, our study is the first to show that both members of a pair vocally interact during the dawn chorus. Given that many temperate-zone bird species have similar life histories as the Great Tit, it is very likely that similar interactive behavior occurs in other (song)birds. This interactive behavior may provide a new and manipulable tool for testing hypotheses about the dawn song and can be used as a future bioassay of male vocalizations.

Habitat composition around nesting sites is one of the important factors that drive the colonial dynamics of waterbirds. Using a Monte Carlo procedure, we compared the changes that occurred over a period of 25 years (1975-1999) in (1) the distribution and composition of tree-nesting heron colonies and (2) the distribution and amount of rice cultivated in the Camargue region of southern France. During the period of 1967-1999, 25 sites in the Camargue were each occupied for at least one breeding season by colonies of tree-nesting herons. Total number of nests, number of nests per colony, and number of colonies varied among the four species considered. During the same period, the proportion of the study area planted with rice fluctuated widely. Overall, nests of all species tended to be located at sites surrounded by a large area of rice fields. However, examination of the results revealed a difference among species in selection of nest colony sites: Cattle Egret (Bubulcus ibis), Squacco Heron (Ardeola ralloides), and Black-crowned Night-Heron (Nycticorax nycticorax) seemed more inclined to nest on sites surrounded by rice fields; whereas Little Egrets' (Egretta garzetta) nest choice was not consistently related to availability of rice fields. That pattern was especially noticeable at a small scale (i.e. <5-km radius around the colony). Our spatial analysis supports previous findings on the effects of rice farming on the colony dynamics of tree-nesting herons. We conclude that different landscape scales are an important consideration for understanding colony site selection and need to be taken into account in the planning and design of agri-environmental development schemes.

I studied summer movements of juvenile Reed Warblers (Acrocephalus scirpaceus) marked as nestlings during four field seasons (1999–2002). To control for birds' movements, nocturnal playback of songs and daytime mist-netting were done. Captures by song playback suggest the existence of nocturnal postfledging movements in Reed Warblers. Birds' age (days) during such movements was found to be 39–52 days. I analyze the temporal schedule and physiological condition of the birds during this period and discuss the mechanism of nocturnal postfledging dispersal and its background and relationships with other events of the annual cycle during the premigratory period.

We conducted an experiment to study the effect of gosling density on food abundance and feeding behavior of Black Brant (Branta bernicla) goslings in two habitat types important to Black Brant on the Yukon-Kuskokwim Delta, Alaska: (1) Carex subspathacea grazing lawns and (2) slough levees that contain Triglochin palustris. Within each habitat, we manipulated grazing pressure by allowing goslings to graze specific plots every 6, 9, or 12 days. We randomly assigned six goslings to one of six treatment groups (three grazing frequencies × two habitats). Biomass of C. subspathacea was higher in lightly grazed plots (grazed every 12 days) than in the heavily grazed plots (grazed every 6 days). Offtake in C. subspathacea was also greater in the lightly grazed plots. Within C. subspathacea stands, proportion of time spent feeding varied among grazing intensities. Goslings within heavily grazed plots spent more time feeding than goslings in lightly grazed plots. Within slough levee habitat, there were no differences between heavily and lightly grazed plots in either biomass or offtake of T. palustris. Whereas overall percentage of time feeding did not vary between the two habitats, percentage of time feeding declined as gosling mass increased in all treatments and habitats. Although the trend in peck rate over time varied among treatments and between habitats, during trials very early in the season we observed a reduced peck rate in the heavily grazed treatment, but only within the C. subspathacea grazing lawns. There was no variation in peck rate among treatments within slough levee habitat; however, peck rates for goslings fed on C. subspathacea was double the rate of goslings in slough levee. Thus, the varied growth responses of plants between habitats to variation in grazing pressure that we observed during this experiment suggest the importance of density-dependent effects on brood-rearing habitat and the resulting variation in gosling growth.

The accuracy with which avian song features indicate phylogenetic relationships has rarely been investigated. In a previous study of vocal evolution in oropendolas (Price and Lanyon 2002a), we estimated the phylogenetic position of the Green Oropendola (Psarocolius viridis) using characters derived from oropendolas' elaborate courtship songs. Here, we test that estimate using mitochondrial DNA sequence data. The position of the Green Oropendola determined from molecular data is remarkably close to that based solely on song characters; both data sets support a close relationship between P. viridis and members of the genus Gymnostinops. Numerous morphological differences yet low genetic divergence among the species in question suggest that rapid diversification has occurred in the group. The fact that this position has not been proposed previously for P. viridis underscores the effectiveness of song characters for phylogenetic reconstruction.

The New World tribe Arini includes 30 genera and represents 148 known species of parrots. A previous phylogenetic study examined nine of those genera and suggested the existence of two groups. Our objective was to better understand the relationships among 14 species from 9 genera belonging to one of those groups. We partially sequenced the 12S and 16S ribosomal DNAs, cytochrome b, cytochrome oxidase I, and control region. We improved our understanding of the phylogenetic relationships among Neotropical parrots by adding both taxa and sequences, but the relationships among the deeper lineages were not well resolved. Our results agree with present classifications that place some species formerly in the genus Ara into three additional genera (Primolius, Orthopsittaca, and Diopsittaca). Additionally, we suggest that (1) D. nobilis and Guarouba guarouba are closely related and the genus Aratinga is not monophyletic; (2) diversification of genera may have occurred during the Miocene, and of species within genera during the Pliocene and Pleistocene; and (3) geologic, climatic, and environmental changes in South America may have been related to that diversification.

We analyzed habitat requirements and selection of Kelp Gulls (Larus dominicanus) breeding at 68 colonies along 2,500 km of coastline in Patagonia, Argentina. Kelp Gulls use a wide range of nesting habitats that include areas with shrub, grass, and herbs which provide different degrees of cover; open ground of various substrate types; and slopes of widely different gradients, confirming the plasticity of the species with respect to habitat recorded elsewhere in the Southern Hemisphere. Eighty percent of the colonies were on islands, the probability of occupation of which increased with distance from mainland and availability of vegetation. Vegetation cover was a key component of nesting habitat for Kelp Gulls in Argentina. Gulls occupied areas with higher cover than random areas; but within vegetated areas, they showed preference for sparser cover that increased visibility and facilitated escape. Kelp Gulls often nested with other species of seabirds and seals and had a positive association with the Olrog's Gull (L. atlanticus).

The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily reflect the opinions of the editors or any official policy of the American Ornithologists' Union.