In urban environments, anthropogenic noise may mask bird song, especially the notes occurring at lower frequencies (1–2 kHz). Birds living in urban environments may modify their songs, particularly the low-frequency portions, to minimize masking by anthropogenic noise. Such modifications have been observed in Great Tits (Parus major) in The Netherlands, as well as in some mammals. We studied Song Sparrows (Melospiza melodia), which are common in both urban and rural environments in much of North America, and recorded the songs of 28 free- living males in Portland, Oregon. We also measured the amplitude and spectrum of ambient noise at singing locations. Song Sparrows singing at noisier locations exhibited higher-frequency low notes and had relatively less energy (amplitude) in the low-frequency range of their songs (1–4 kHz), where most anthropogenic noise also occurred. Although the mechanism(s) producing the correlation are as yet undetermined, the observed match between song and noise may result from behavioral plasticity. We discuss explanations for these patterns and how to test them.

Le Chant de Melospiza melodia Varie avec le Bruit Urbain

Parakeets in the genus Pyrrhura occur in Amazonia and in almost all other major Neotropical forests. Their uneven distribution (with some widespread and several geographically restricted endemic taxa) and complex patterns of plum- age variation have long generated a confused taxonomy. Several taxonomically difficult polytypic species are usually recognized. Here, we present a mitochondrial DNA (mtDNA) phylogenetic analysis of Pyrrhura, with emphasis on the especially problematic picta-leucotis complex, to provide a more robust basis for interpreting the systematics and historical biogeography of the group. Our main findings are that (1) Pyrrhura can be divided into three main evolutionary lineages, one comprising P. cruentata, an Atlantic Forest endemic, the second comprising the picta-leucotis complex, and the third comprising the remaining species; (2) the traditionally recognized species P. picta and P. leucotis are not monophyletic; and (3) most of the species recognized by Joseph (2000, 2002) are diagnosable as independent evolutionary units, with the exception of the following species pairs: P. snethlageae and P. amazonum, P. leucotis and P. griseipectus, and P. roseifrons and P. peruviana. Other than P. cruentata, the two clades that constitute Pyrrhura appear to have radiated and evolved their present mtDNA diversity over short periods during the Plio-Pleistocene.

Sistemática Molecular y Patrones de Diversificación en Pyrrhura (Psittacidae), con Énfasis en el Complejo Picta-Leucotis

We assessed potential effects of introduced Norway rats (Rattus norvegicus) on Least Auklets (Aethia pusilla) breeding at Sirius Point on Kiska Island, the largest auklet colony in the Aleutian Islands, Alaska. We compared productivity, chick growth, and adult survival of Least Auklets during 2001-2003 at Kiska and two nearby, rat-free Least Auklet colonies on Buldir and Kasatochi islands. During 2001 and 2002 (when rats were abundant), productivity at Kiska was the lowest ever recorded for this species (0.09–0.16 chicks fledged per eggs laid), primarily because of high mortality of newly hatched chicks. Growth rates and mean fledging mass were both lower on Kiska than on rat-free islands, though there were some interannual differences in these patterns. Adult survival rates were highly variable among years but strongly concordant among colonies, and survival from 2001 to 2002 on Kiska (0.881 ± 0.033) did not differ significantly from long-term averages on either Buldir (0.853 ± 0.014, 1990-2003) or Kasatochi (0.893 ± 0.027, 1996-2003) islands. Although we found little evidence at nesting crevices of predation on adults, eggs, or chicks, low productivity and slow chick growth were both consistent with disturbance caused by rats, particularly through disruption of adults attempting to brood or provision young chicks. Breeding failure may have been exacerbated by low prey availability for chick provisioning, but the lack of concordance in either productivity or chick growth rates between Kiska Island and nearby rat-free Buldir Island cast doubt on this possibility.

Évaluer les Effets de Rattus norvegicus Introduits sur la Survie et la Productivité de Aethia pusilla

We describe a method for surveying birds in river habitats that allows for rapid assessment across broad spatial scales and estimation of detection probabilities. Our river survey approach incorporates a double-survey technique, whereby observers in two canoes simultaneously survey birds along a river reach. Data are in the form of a two-sample mark-recapture history, and covariates suspected of influencing detection probabilities can be included in the modeling process and evaluated using information-theoretic approaches. We provide an example using the method along the Madison and upper Missouri rivers in Montana. Overall, detection probabilities for each observer ranged from 57% to 89%, and combined detection probabilities (the likelihood of at least one observer detecting an individual) were consistently high (88% across all species). Detection probabilities across species were positively correlated with body mass. Detection probabilities for some species were influenced by observer, river conditions, and whether species were in groups or alone; groups were more detectable, and individuals in slow-flowing and wide sections of river were more detectable. Boat-based double surveys are a viable method for estimating detection probabilities of birds in river habitats, and double surveys should be considered in other aquatic

Estimaciones de Probabilidades de Detección de Aves de Río Utilizando Muestreos Dobles systems.

Many species of birds start incubation before the last egg of a clutch is laid, which often results in asynchronous hatching and fledging. The incubation pattern favored by natural selection should lead to greater reproductive success than alternative patterns. Equations for calculating the reproductive success of a clutch as a function of the start of incubation have been proposed by Clark and Wilson (1981) and Hussell (1985). Both equations predicted a greater frequency of an earlier start of incubation than occurs in nature. Here, I present a new equation in which the relevant parameters determining reproductive success as a function of the start of incubation are (1) the probability of any young leaving a nest and (2) the post-first- fledging daily survival rates of the remaining nestlings. This equation is universally applicable and accounts for the greater frequency of incubation starting later, rather than earlier, in the laying sequence of most birds. I use the equation to evaluate various hypotheses regarding the evolution of incubation patterns.

Una Nueva Ecuación para Calcular el Éxito Reproductivo de Nidadas en Función del Día en que Comienza la Incubación: Algunas Implicaciones

In birds, relative growth rates of morphological characters change in response to restricted food intake during development. Differential allocation of limited resources is hypothesized to reflect functional priorities for developing chicks. Body mass, wing, and flight feathers have been identified as potential priorities for seabird chicks. We used allometry to examine allocation in captive Common Murre chicks fed within a range of natural provisioning. During days 10–45 post-hatch, chicks were fed one of four diets that varied in biomass, energy content, and composition. Energy intake had a more profound effect on growth and development than diet composition; it significantly reduced absolute growth of body mass, manus, and tarsus. Between day 15 and day 20, allocation changed in all treatments: growth of manus was maintained at the expense of body mass. Chicks in more restricted treatments shifted allocation to manus at a lower body mass than those in less restricted groups, but subsequently allocated similarly. Wing loading was higher for chicks than for adult alcids, but scaled similarly. Growth of primary feathers was the most sensitive to small differences in diet composition. Our data also suggest that some changes in allocation may be ontogenetically determined rather than part of an adaptive response to reduced food intake.

Croissance et Allocation chez des Oisillons Uria aalge

Point counts are the method most commonly used to estimate abundance of birds, but they often fail to account properly for incomplete and variable detection probabilities. We developed a technique that combines distance and double-observer sampling to estimate detection probabilities and effective area surveyed. We applied this paired-observer, variable circular-plot (POVCP) technique to point-count surveys (n = 753) conducted in closed-canopy forests of southeast Alaska. Distance data were analyzed for each species to model a detection probability for each observer and calculate an estimate of density. We then multiplied each observer's density estimates by a correction factor to adjust for detection probabilities <1 at plot center. We compared analytical results from four survey methods: single-observer fixed-radius (50-m) plot; single-observer, variable circular-plot (SOVCP); double-observer fixed-radius (50-m) plot; and POVCP. We examined differences in detection probabilities at plot center, effective area surveyed, and densities for five bird species: Pacific-slope Flycatcher (Empidonax difficilis), Winter Wren (Troglodytes troglodytes), Golden-crowned Kinglet (Regulus satrapa), Hermit Thrush (Catharus guttatus), and Townsend's Warbler (Dendroica townsendi). Average detection probabilities for paired observers increased ≈8% (SE = 2.9) for all species once estimates were corrected for birds missed at plot center. Density estimators of fixed-radius survey methods were likely negatively biased, because the key assumption of perfect detection was not met. Density estimates generated using SOVCP and POVCP were similar, but standard errors were much lower for the POVCP survey method. We recommend using POVCP when study objectives require precise estimates of density. Failure to account for differences in detection probabilities and effective area surveyed results in biased population estimators and, therefore, faulty inferences about the population in question.

Estimaciones de la Densidad y de las Probabilidades de Detección a Partir de Muestreos Utilizando Conteos en Puntos: Una Combinación de Muestreos de Distancia y de Doble Observador

The ultimate success of reintroduction programs for endangered species depends on the ability of reintroduced animals to breed in the wild. We studied the nesting success and breeding biology of a reintroduced population of Puaiohi (Myadestes palmeri) on the island of Kaua'i, Hawaii. Thirty-four captive-bred Puaiohi were released into the Alaka'i Swamp in 1999-2001 and monitored using radiotelemetry. Ten females and two males paired with wild and other released birds, including one polygynous trio. From March to September, 31 nests were built. Mean clutch size was 2.0 eggs, daily nest survival was 0.97 ± 0.01 (mean ± SE) and overall nest success was 0.40 ± 0.02. We confirmed predation, most probably by rats (Rattus spp.), as the greatest cause of nest failure, occurring at 38% of active nests with known fates, and causing the death of two nesting adult females. Ground-based rodent control proved ineffective at protecting nest attempts. Successful nests fledged an average of 1.4 young each (n = 10), and 85% of fledglings survived at least two weeks. Importantly, breeding behavior and success were comparable to those of wild Puaiohi. This is the first record of breeding in the wild from captive-bred endangered Hawaiian passerines. The ability of captive-bred Puaiohi to survive and breed successfully in the wild bodes well for future releases of this and other endangered passerines, but high predation rates on nests and nesting females highlights the importance of maintaining and restoring safe habitat for recovery.

Biología y Éxito Reproductivo de una Población Reintroducida de Myadestes palmeri, una Especie en Peligro Crítico

We studied the effects of chronic avian malaria (Plasmodium relictum) infections on the reproductive success of a native Hawaiian honeycreeper, Hawaii Amakihi (Hemignathus virens). Chronic malaria infections in male and female parents did not significantly reduce reproductive success as measured by clutch size, hatching success, fledging mass, number of nestlings fledged, nesting success (daily survival rate), and minimum fledgling survival. In fact, nesting success of pairs with chronically infected males was significantly higher than those with uninfected males (76% vs. 38%), and offspring that had at least one parent that had survived the acute phase of malaria infection had a significantly greater chance of being resighted the following year (25% vs. 10%). The reproduction and survival of infected birds were sufficient for a per-capita population growth rate >1, which suggests that chronically infected Hawaii Amakihi could support a growing population.

Efectos de las Infecciones Crónicas de Malaria Aviaria (Plasmodium relictum) en el Éxito Reproductivo de Hemignathus virens

A correlation between length of telomere restriction fragments (TRFs) and age has recently been demonstrated in several bird species. Comparisons of different-aged individuals within a population have shown that TRFs typically shorten with age and that this shortening continues throughout the life span of the species. In addition, it has been shown that telomere rate-of-change (TROC) correlates tightly with life span across several bird species. Previous studies of long-lived birds, however, have shown exceptions to these trends, demonstrating no declines in TRF length in adults in some cases and increases in TRF length with age in other cases. Here, we report known ages of individuals from a colony of Great Frigatebirds (Fregata minor) based on recaptures of leg-banded birds, including two individuals that were at least 44 years of age, the oldest Great Frigatebirds ever reported. Using a previously developed molecular technique, we report a predictable, nonlinear decline of TRF length with age in this population. Telomere restriction fragments decline more rapidly early in life but continue to shorten throughout the life span examined. The rate of decline in TRF for this species does not fit the tight correlation previously reported between TROC and life span in other species. Finally, we tested the ability to estimate age and age structure of breeding females on the basis of the calibration of TRF length and individuals of known age. Because of the slow telomere-attrition rate and the variability observed in TRF lengths at given ages, estimations of age of individuals and of estimated age structure of breeding birds in this population are not particularly reliable.

Encogimiento del Telómero en un Ave Marina Longeva: Análisis de Secciones Cruzadas y Evaluación de una Herramienta de Envejecimiento

Theory suggests that the persistence of metapopulations will be influenced by the degree of synchrony in the dynamics of their component populations. Various studies have shown that climate can promote synchrony in the size of adjacent populations linked by dispersal, but fewer studies have examined the effects of climate on underlying demographic rates. We studied annual variation in the timing of breeding and reproductive rates in Song Sparrow (Melospiza melodia) on islands linked by dispersal to determine whether biotic factors acting at local scales or climatic factors acting at a regional scale were more influential of variation in demography. The onset of egg laying varied markedly among years but was roughly synchronous across islands within years. Despite this synchrony, island populations varied markedly in reproductive rate, mainly from spatial variation in nest depredation and brood parasitism. In general, populations farther from Vancouver Island and with fewer resident predators experienced less nest depredation and brood parasitism, and higher reproductive rates, than populations closer to Vancouver Island. Our results show that even when climate acts regionally to synchronize reproductive timing in adjacent populations, its effects on reproductive rate may be overridden by biotic factors that vary among populations.

Depredación de Nidos, Parasitismo de Cría y Variación Reproductiva en Poblaciones Isleñas de Melospiza melodia

Although most habitat characteristics are known to be continuously variable in space, practicality dictates that most habitat-selection studies at the spatial scale of the territory treat within-territory habitat as essentially homogeneous. However, the limitations associated with such a compromise have remained largely unexamined. Male Cerulean Warblers (Dendroica cerulea) exhibit nonrandom space- use patterns within their territories, in that all territories contain areas of intensive use or core areas. In addition to documenting territory-wide habitat and behavioral use patterns in this species, we asked two specific questions about core-area structure and function. (1) Are core-area habitats distinct in their vegetative composition and structure from the rest of the territory? (2) What behavioral mechanisms underlie the nonrandom space-use patterns? On a territory-wide basis, males used trees in proportion to their availability; however, core areas were predominantly composed of bitternut hickory (Carya cordiformis), which was a highly preferred song-post tree. Core areas were not consistently associated with any other habitat feature, including canopy gaps. Core areas were singing centers; song-post densities within core areas were 10× higher than in noncore areas. In our study area, bitternut hickories have significant delayed leaf-out patterns, potentially offering minimal acoustic hindrance to song transmission until late in the breeding season. These singing centers may be strategically placed to simultaneously maintain vigilance over social nests and maximize communication with conspecifics. Core areas are potentially as important to males as nesting habitat is to females, and their provision should be taken into account when implementing conservation or management strategies.

Uso de Hábitat en los Territorios y Selección de Microhábitats por los Machos en Dendroica cerulea

Much of our current understanding of the demographic effects of habitat fragmentation on bird populations is derived from studies of passerines in forests and tallgrass prairie surrounded by woody vegetation. We quantified grassland bird density, nest survival, and productivity in 41 native mixed-grass prairie pastures during 1997-2000 in southern Saskatchewan, Canada. Pastures ranged in size from 18 ha to 11,600 ha and were typically surrounded by agriculture (i.e., ranching and annual cropping). Grassland passerines did not respond strongly or uniformly to patch size. Sprague's Pipit (Anthus spragueii) was the only species whose density increased with pasture size. Patch size had minimal influence on nest survival of Sprague's Pipit or Clay-colored Sparrow (Spizella pallida); whereas nest survival increased with patch size for Savannah Sparrow (Passerculus sandwichensis) and declined for Baird's Sparrow (Ammodramus bairdii), Chestnut-collared Longspur (Calcarius ornatus), and Western Meadowlark (Sturnella neglecta). Time-specific factors (i.e., nest age, date, and year) were more important predictors of nest survival than patch size. Exploratory analyses indicated that effects of edge distance, pasture shape, or landscape on nest survival were just as likely as patch-size effects. However, effects of edge on Chestnut-collared Longspurs may be governed by landscape-level factors, because nest survival decreased with distance to edge in landscapes with increased amounts of cropland. Our results indicate that mixed-grass prairie parcels ≥18 ha play a role in the conservation of several grassland passerine species currently in decline, but the conservation of Sprague's Pipit likely depends on maintaining larger tracts of native prairie.

Les Passereaux des Prairies Herbacées Montrent des Réponses Faibles et Variables en Réponse à la Taille des Parcelles d'Habitats

Analysis of stable hydrogen isotope ratios in feathers (δD_f) is a promising method for investigating population connectivity in migratory birds. Stable hydrogen isotope ratios in precipitation (δD_p) vary across North America with respect to latitude, elevation, and seasonal air-mass trajectories. A strong relationship between δD_f and δD_p at locations of feather growth has been documented for several bird species. Some studies have used measurements of δD_f to plot the origins of migrants on maps of long-term weighted-average, growing-season North American δD_p (hereafter “δD_p maps”) using the observed relationship between δD_f and δD_p from a reference sample of known-origin birds. The accuracy of this method depends on the strength of the δD_f and δD_p relationship and accuracy of the δD_p maps. Recently, a high-resolution (1-km²) model of North American δD_p was published (Meehan et al. 2004) that accounts for the effect of elevation on δD_p where previous models did not. We compared δD_f measurements from a geographically diverse sample of 264 raptor feathers with δD_p estimates for feather-sample locations. We documented a strong relationship between raptor δD_f and δD_p across North America. However, we also documented substantial regional variation in this relationship. We created a “base map” of North American raptor δD_f that incorporated the regional variation described by our sample. We plotted δD_f values from migrant Sharp-shinned Hawks (Accipiter striatus) captured in eastern Nevada directly on this map to demonstrate how it can be used to view the origins of migrants.

Un Procedimiento Basado en Sistemas de Información Geográfica para Estimar el Origen de las Aves Rapaces Migratorias en Norte América Usando los Cocientes de Isótopos Estables de Hidrógeno Presentes en las Plumas

Concentrations of plasma metabolites, including triglyceride, glycerol, and B-OH butyrate, can be used to determine refueling performance of migratory birds. We tested the effects of diet type and diet lipid content on the predictive relationships between metabolites and body mass changes in three species of passerines in captivity. In addition, we tested whether measurement of plasma phospholipids improved predictions of mass change. Rate of mass change was positively related to triglycerides in a captive frugivore (Cedar Waxwing; Bombycilla cedrorum) and a granivore (White-crowned Sparrow; Zonotrichia leucophrys). B-OH butyrate was negatively and nonlinearly related to mass change in Cedar Waxwings and White-crowned Sparrows. Glycerol was negatively related to mass change in Cedar Waxwings but not in White-crowned Sparrows. Mass change was positively related to triglycerides and negatively related to B-OH butyrate in Yellow-rumped Warblers (Dendroica coronata). There was no effect of diet lipid content (9% vs. 28% dry mass) on these predictive relationships. Plasma phospholipids were positively related to mass change in White-crowned Sparrows, but negatively related to mass change in Yellow-rumped Warblers and not related to mass change in Cedar Waxwings. Measurement of phospholipids did not improve prediction of mass change by metabolite profiles. Nevertheless, plasma metabolite profiles are predictive of short- term mass changes in captive birds regardless of diet type or diet lipid content, and can provide valuable information on refueling performance in studies of stopover ecology.

Efectos de la Dieta sobre las Predicciones de los Cambios en el Peso Corporal de Aves por medio de Metabolitos Plasmáticos

Most studies of cooperatively breeding species have revealed that indirect fitness gains from helping are lower than benefits gained from direct reproduction. Exceptions to this “best of a bad job” strategy are rare. Brown Jays (Cyanocorax morio) in Monteverde, Costa Rica, live in large groups (mean = 10 individuals) and have never been observed to breed as unaided pairs. Helpers provide a substantial percentage (70%) of all nestling feedings. Together, these observations suggest that helping may be crucial for reproductive success in this population. We used multivariate models to examine the effect of helpers on offspring production using a long-term data set. Data on nest-site success and brood reduction suggested that predation was the major cause of nesting failure. Nesting in an isolated tree was the major determinant of successful nestling production, and our data indicate that small groups (less than 9 individuals) may not be able to acquire or defend territories that contain suitable nesting sites. The number of juveniles (young surviving 30 days after leaving the nest) and yearlings was positively related to group size, even after removing groups that nested only in non-isolated trees. Small groups were also more likely than large groups to have total reproductive failure in a season. Helpers may increase juvenile survival by reducing predation, increasing juvenile condition, or providing learning opportunities for foraging and antipredator behaviors. Helpers on their natal territories receive some indirect benefits, though these are low compared with independent breeding. Immigrant male helpers may benefit primarily by gaining future breeding opportunities. Delayed benefits related to territory inheritance and dispersal coalitions may be the best explanation for helping in this population.

Efectos de los Ayudantes sobre la Producción de Progenie en Cyanocorax morio, una Especie con Cría Cooperativa

Since the 1950s, flipper bands have been used widely to mark penguins (Spheniscidae), but not without concerns regarding possible negative effects on survival and fitness. As part of a demographic study of Adélie Penguins (Pygoscelis adeliae) in the western Ross Sea, Antarctica, we investigated effects of flipper bands on foraging-trip duration and food loads, as well as apparent survival, during four breeding seasons (2000-2003), using mark-recapture and radio-frequency identification (RFID) technology. Foraging-trip durations were ∼8% (3.5 h) longer, on average, for banded compared with unbanded birds, but the effect varied among years. Food loads did not differ between banded and unbanded birds, but males carried heavier food loads than females. Flipper bands decreased apparent annual survival by 11–13% during 2000-2003, but over a longer time period (1996-2003) we observed high annual variability, including years of high survival for banded birds. Males had slightly higher survival than females in both banded and unbanded birds. Mechanisms resulting in band effects on foraging behavior and survival, the variable effect of bands by season, and the potential ameliorating effect of age or experience on the effects of bands need further investigation in Adélie and other penguin species. We recognize a need to understand and balance the negative consequences of flipper bands for penguins against the beneficial gains in information associated with their use.

Effets du Baguage à l'Aileron sur le Comportement de Recherche Alimentaire et la Survie de Pygoscelis adeliae

Recent studies suggest that a linear correlation exists between the age of individual birds and accumulation of the advanced glycation endproduct pento- sidine (Ps). We compared Ps accumulation in skin tissue of Ruffed Grouse (Bonasa umbellus) and Double-crested Cormorants (Phalacrocorax auritus). Skin samples were taken from the breasts of 52 Ruffed Grouse of known ages ranging from a few days to 10 years. Skin was cleaned of feathers and adipose tissue, acid hydrolyzed, and measured for collagen content via hydroxyproline spectrophotometric assay. Pentosidine concentrations were determined using reverse-phase high-performance liquid chromatography. Fluorescent detection (excitation: 310 nm, emission: 385 nm) revealed that concentrations of Ps per milligram of collagen increased curvilinearly with age (r² = 0.87, P < 0.0001). Additionally, a blind study of 19 Double-crested Cormorants revealed a linear relationship between Ps concentrations and age (r² = 0.93). Comparison of these two species revealed a more rapid accumulation of Ps in Ruffed Grouse. Accurate age information could aid species recovery programs and provide insights into longevity, now understood entirely from banding programs and captive birds.

Comparación entre Especies de la Acumulación de Pentosidina y su Correlación con la Edad de las Aves

The postfledging dependence period is not well documented for many species of raptors, including Golden Eagles (Aquila chrysaetos). From 1997 to 1999, we used satellite telemetry to estimate the length of the postfledging dependence period, and the finite survival rate of fledglings during that period, for migratory Golden Eagles in Denali National Park and Preserve, Alaska. Length of the postfledging dependence period averaged 50.1 days and ranged from 39 to 63 days. The post- fledging dependence period was longer for Golden Eagles that hatched earlier, but hatching date did not influence the date they departed their natal area. Average date of departure from the natal area was 25 September. The departure period spanned a 17-day period from 15 September to 5 October, and coincided with a series of environmental changes including decreases in day length, temperature, and prey diversity. Probability of survival during the postfledging dependence period was 0.98 (95% CI = 0.94 to 1.00).

Período de Dependencia Posterior al Emplumamiento de Aquila chrysaetos en el Parque Nacional y Reserva Denali, Alaska

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.

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.

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.

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.

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.