We began our studies of House Sparrow (Passer domesticus) biparental care in the mid-1990s by applying the classic Margaret Morse Nice field technique of color-banding individuals. Over the ensuing summers, we slowly accumulated quantitative provisioning records for 100 broods, even as we commenced a series of experimental manipulations. Provisioning data showed parental fitness, as expressed by offspring recruitment into the local breeding population, to be shaped mainly by the adults' ability to deliver enormous insect prey items. It also turned out that production of robust and competitive fledglings routinely involves losing one or more nestlings (brood reduction in 42% of 1,000 multi-chick families). Recruitment success was compensated for the death of an offspring if the subsequent reallocation of food enables surviving nest-mates to gain at least 2 g more before fledging. Video samples showed that parents of day 3 broods favored larger siblings, even though brood reduction typically occurs on ∼day 4, suggesting that adults participate actively in promoting some offspring over others. The social dynamic affecting how parents work as a team during provisioning does not fit the pattern expected if partners negotiate actively with one another, but points more toward the likelihood of “sealed bids.” Specifically, experimental handicapping of individual parents (tail-weights and hormone implants) indicates partners operate quite independently during brood-rearing. We are now extending our experiments into the incubation phase, where parents are probably better-informed about partner activities, thus potentially able to adjust to fluctuating contributions. Finally, behavioral rules affecting food deliveries seem to differ for females and males. Females normally increase provisioning as the brood ages, but males do not. However, when broods received supplemental nutrients, males matched the female upsurge, accelerating their deliveries by 25%, showing they usually work well below capacity.

Eared Grebes (Podiceps nigricollis) in autumn make a postbreeding/molt migration from breeding areas in western North America to hypersaline lakes in the Great Basin. We studied their biology in 2001–2006 during this phase of the annual migration near Green River, Wyoming, USA where migrants en route to Great Salt Lake, Utah land on industrial ponds. Most evidently originate in the Prairie Pothole Region of North Dakota. The main movement extends from late July to mid-October. Migrants arrive almost daily with the cumulative percentage of transiting birds increasing by about 1% per day. Adult males and females migrate on the same schedule and precede juveniles by 2–3 weeks. Annual differences in phenology, abundance, age ratio, and wing molt vary with availability of wetland habitats in the main source area. Data on mass, body composition, energetics, and stomach contents indicate a typical flight involves a direct 2–3 day non-feeding migration, which is accomplished at night. Grebes are quiescent during the day and do not resume their migration until 45 min after sunset. We documented two undescribed vocalizations, a short-range contact note and one associated with departure. The possibility that Eared Grebe productivity, as inferred from studies of migrants through Wyoming, can provide insight into the status of waterbirds in the source area is worth further investigation.

Natal dispersal is common among many bird species with females usually dispersing farther than males. We examined postfledging and natal dispersal ecology of Crested Ibis (Nipponia nippon) in the Qinling Mountains, China by marking nestlings with either color bands or radio transmitters. Family groups, consisting of juveniles after fledging and their parents, dispersed progressively farther from nest sites after fledging in a southerly direction with a mean (± SD) direction of 189.2 ± 46.5° and a mean distance of 20.3 ± 7.0 km. Mean natal dispersal distance of females (9.6 km) was significantly greater than for males (5.9 km) (t  =  2.14, P  =  0.03). Most individuals moved southeasterly from natal areas and dispersal movements of individual ibis were concentrated at the mean direction (μ  =  185.6°, š  =  86.1°). First reproduction by females (3.64 ± 1.36 years) was not significantly earlier than for males (4.17 ± 1.47 years). The results of this study will be useful for reintroduction programs for critically endangered species.

We attempted to distinguish spring passage migrant Tropical Kingbirds (Tyrannus melancholicus) from resident conspecifics where they overlap in South America. Migrant males at our Bolivian study site had significantly less tail feather molt and longer wing chords than resident males. Migrant females had significantly longer wing chords, less flight feather molt, and less flight feather wear than resident females. We found no evidence of genetic population differentiation between migrants and residents. We also compared wing chords of migrants and residents to those of breeding kingbirds in breeding populations further south. Wing chords of migrants were more similar to those of breeders from further south than to those of breeders at our study site. An ability to distinguish migrant from resident conspecifics will be critical to understanding migrant winter ecology, migratory routes, and connectivity of migratory populations in South America.

The Red-cockaded Woodpecker (Picoides borealis) is an endangered species endemic to pine (Pinus spp.) forests of the southeastern United States. I examined Red-cockaded Woodpecker foraging behavior to learn if there were male/female differences at the Savannah River Site, South Carolina. The study was conducted in largely young forest stands (<50 years of age) in contrast to earlier foraging behavior studies that focused on more mature forest. The Red-cockaded Woodpecker at the Savannah River site is intensively managed including monitoring, translocation, and installation of artificial cavity inserts for roosting and nesting. Over a 3-year period, 6,407 foraging observations covering seven woodpecker family groups were recorded during all seasons of the year and all times of day. The most striking differences occurred in foraging method (males usually scaled [45% of observations] and females mostly probed [47%]), substrate used (females had a stronger preference [93%] for the trunk than males [79%]), and foraging height from the ground (mean ± SE foraging height was higher for males [11.1 ± 0.5 m] than females [9.8 ± 0.5 m]). Niche overlap between males and females was lowest for substrate (85.6%) and foraging height (87.8%), and highest for tree species (99.0%), tree condition (98.3%), and tree height (96.4%). Both males and females preferred to forage in older, large pine trees. The habitat available at the Savannah River Site was considerably younger than at most other locations, but the pattern of male/female habitat partitioning observed was similar to that documented elsewhere within the range attesting to the species' ability to adjust behaviorally.

Foraging habits and habitats of exclusive aerial insectivores, the Edible-nest Swiftlet (Aerodramus fuciphagus inexpectatus) and Glossy Swiftlet (Collocalia esculenta affinis), were studied in Andaman Islands, India. Observations were made during January to June 2004 between 0500 and 1800 hrs at four locations in the forest and on open paddy land. Edible-nest and Glossy swiftlets, respectively, spent (x¯ ± SD) 17.2 ± 11.4% and 25.8 ± 15.6% of their time foraging with significant temporal variations. Glossy Swiftlets had spatial variations in twist, flutter, and tail-wing-open foraging maneuvers. This species also had diurnal variations in flock size, which were positively correlated with feeding attempts. Both swiftlets shared all microhabitats except Inside Forest Canopy and Inside Stream Bank Canopy. Microhabitat use did not vary significantly in Below Stream Bank Canopy, >10 m Above Forest Canopy, >30 m Above Ground, and Above Forest Canopy for Edible-nest Swiftlets. Inside Forest Canopy and Inside Stream Bank Canopy categories for Glossy Swiftlets were relatively important in descending order. Deforestation near and distant from caves used by swiftlets for breeding in the islands can severely affect the wild population of both species.

We analyzed phenotypic distribution, nesting success, and genetic purity of Golden-winged Warblers (Vermivora chrysoptera) and Blue-winged Warblers (V. pinus) in two ecologically distinct nesting habitats: early-succession uplands, and swamp forests. The proportion of phenotypically pure Golden-winged Warblers in swamp forests (94%) differed significantly from uplands (53%) as did the proportion of Golden-winged Warbler pairs (93%) in swamp forests compared to uplands (48%). Only 1% of the phenotypically pure Golden-winged Warblers in swamp forests paired with either a hybrid or a Blue-winged Warbler, but 7% of the phenotypically pure Golden-winged Warblers in uplands formed a hybrid pair. The probability of nesting success for Golden-winged Warbler pairs in swamp forests (65%) was significantly higher than in uplands (37%). Mitochondrial DNA analyses indicate that all 10 phenotypically pure Golden-winged Warblers sampled from swamp forests had the ancestral Golden-winged Warbler haplotype, while 10 of 25 Golden-winged Warblers from uplands had the ancestral Blue-winged Warbler haplotype (P  =  0.033). Swamp forests may provide a source habitat for Golden-winged Warblers with a high phenotypic and genotypic purity even in sympatry with Blue-winged Warblers.

We examined the effect of geographic isolation on morphology, genetic structure, and abundance of the Sooty-capped Bush Tanager (Chlorospingus pileatus), an endemic species restricted to highlands of Costa Rica and western Panama. Abundance and morphology were measured at five study sites and genetic variation was calculated from three microsatellite loci. We expected geographic discontinuities in this species' distribution to have an effect on its morphology and genetic structure. Genetic variation was higher within than between populations with no effect of geographic barriers on population genetic divergence in this species, indicating gene flow is high between populations. Unique alleles were detected in each population and F_st values increased with geographic distance between populations. Some morphological traits differed between populations, which may be caused by adaptation to different selective pressures in each population. Molecular data did not differ between the two color morphs that coexist in two isolated populations, which were considered different species.

We examined a 35-year transition in the breeding bird community at a successional study site in a reforesting landscape in southwestern New York, USA. Changes in the successional plot were compared with those in two additional census plots, one in undisturbed forest and the other in a managed tree farm. The territories of 7,429 singing male songbirds were mapped on the census plots. The most dramatic changes in community structure were in the successional plot where total number of territories declined between the beginning of the study (x ¯  =  95.8 territories, 1969–1973) and end of the study (x ¯  =  57.2 territories, 1999–2003); grassland/shrub nesting species were nearly extirpated, and the number of neotropical migrant territories increased from zero in 1969 to 30 in 2003. The average number of neotropical migrant territories in the undisturbed forest plot declined from the beginning of the study (x ¯  =  54.0, 1975–1979) to the end (x ¯  =  44.8, 2003–2007). The average number of territories increased in the managed tree farm from the beginning of the study (x ¯  =  53.6, 1983–1987) to the end (x ¯  =  104.0, 2003–2007) largely due to increases in abundance of temperate zone migrants and resident species. Counts of individual species in the census plots were not highly correlated with counts from regional Breeding Bird Survey routes.

We examined the influence of shoreline residential development on breeding bird communities along forested portions of Lake Superior and hypothesized that anthropogenic changes related to housing development would alter bird community structure compared to areas without human development. We used point counts to compare relative abundance of bird species in relation to residential development at coarse (along 1 km shoreline stretches with and without housing/cottage development) and fine (developed and undeveloped sides of a shoreline access road) spatial scales during the 2005 breeding season. More species had development related differences in abundance at the finer-scale analysis than at the coarse scale. American Crows (Corvus brachyrhynchos) and American Robins (Turdus migratorius) were more abundant on the developed, shoreline side of shoreline access roads. Red-breasted Nuthatches (Sitta canadensis), Black-throated Green Warblers (Dendroica virens), and Red-eyed Vireos (Vireo olivaceus) were more abundant on the undeveloped, inland side of shoreline access roads. Several species were detected exclusively in developed or undeveloped forest areas. The pattern of development-related differences in relative abundance of bird species depended on the scale at which data were analyzed, suggesting that many species may respond to habitat differences within the 100 m scale quite distinct from how they respond to differences at the scale of thousands of meters.

We monitored songbird nest survival in two reforesting, ∼50-ha former cropland sites along the Missouri River in central Missouri from 2001 to 2003. Sites were partitioned into three experimental units, each receiving one of three tree planting treatments. Nest densities varied among restoration treatments for four of five species, but overall nest survival rates did not. Nest survival varied with day-of-year and with incidence of brood parasitism by Brown-headed Cowbirds (Molothrus ater). Nest survival was higher early and late in the season, and parasitized nests experienced lower nest survival, despite few complete losses directly attributable to parasitism. Probability of parasitism was inversely related to distance to the nearest tree, and was much lower than in old field study sites in the same region. High cowbird parasitism frequencies are usually associated with landscapes low in forest cover, yet these sites in an agriculturally-dominated bottomland landscape experienced low (∼0.8–24%) cowbird parasitism. The assumed negative relationship between landscape-level forest cover and cowbird parasitism needs further study in habitats other than forest.

We examined whether male plumage coloration signals parental quality in the American Redstart (Setophaga ruticilla), a highly ornamented, migratory warbler. We measured the relationship between both adult male arrival date and phenotype (morphology, melanin- and carotenoid-based plumage), and parental care levels of both parents. Males with brighter flank feathers made more visits to the nest and spent more time at the nest, consistent with the ‘good-parent hypothesis’. Female parental care (number of visits) was negatively correlated with intensity of red of her mate's tail feathers and positively associated with her mate's parental effort. These data indicate offspring of brighter males receive more care from both parents. Our results suggest carotenoid-based plumage traits of male American Redstarts may have an important role in intersexual signaling, and add to our understanding of the evolution of multiple ornaments.

Biologists know relatively little of how one of the most important avian phenotypic signals, feather coloration, may be affected by anthropogenic changes resulting from urbanization. We examined the relationship between urbanization and carotenoid-based plumage color of Northern Cardinals (Cardinalis cardinalis) in 13 riparian forests distributed across a rural-to-urban landscape gradient in central Ohio, USA. Feathers and morphometric measurements were collected from breeding territorial males (n  =  129) and females (n  =  145) during March–August 2006–2008. Plumage brightness of males, but not females, increased with body condition (i.e., size-adjusted mass) and declined with amount of urbanization surrounding forests in which cardinals bred. The extent plumage coloration reflected condition was partially mediated by landscape composition. Specifically, the relationship between brightness and body condition was most pronounced in the most rural landscapes. The interdependency of male coloration and body condition may be more relaxed in urban than rural landscapes if carotenoid-rich foods from anthropogenic and/or invasive sources are more available, or are accessible to birds across a wide range of condition.

We studied the breeding ecology of the Southern Grey Shrike (Lanius meridionalis) at the Shezaf Nature Reserve, Arava Valley, Israel, an extremely arid desert with mean annual rainfall of 30 mm. We color-banded 128 shrikes during 2007–2009. The breeding season lasted from late February until late June. We found 34 nests and a correlation between years with amount of precipitation and number of breeding pairs. Second broods after successful broods were found only in 2007 and were all unsuccessful. Most nests were in Acacia trees; pairs that nested in dry trees, lacking foliage, were more likely to fail. The average clutch size was 3.44; average number of nestlings was 1.95; and average number of nestlings that fledged was 1.24. These results are lower than other studies of the species, probably a result of the scarcity of food in the arid environment. Nest survival rate was higher during incubation than during rearing of nestlings (0.71vs. 0.62), and total nest survival was 44.5%. The arid Arava Valley influences breeding success of Southern Grey Shrikes, and the present severe drought could negatively influence persistence of the shrike population in the Arava Valley.

Nelson's (Ammodramus nelsoni) and Saltmarsh (A. caudacutus) sparrows are sympatric breeders in tidal marshes of the southern Gulf of Maine. These sparrows hybridize, have different mating strategies, and males do not defend territories or provide parental care. We estimated and compared core area sizes, home range sizes, and habitat use between species and between males and females. We radio-marked 140 sparrows (63 Nelson's and 77 Saltmarsh sparrows) during three breeding seasons (1999–2001) at Scarborough Marsh, Maine, USA. Home ranges of male A. nelsoni were 2.3 times larger (± SE) (119.68 ± 19.43 ha) than those of male A. caudacutus (52.85 ± 8.68 ha). Home range sizes of female Nelson's and female Saltmarsh sparrows did not differ from each other (female Nelson's home range  =  43.58 ± 13.10 ha; female Saltmarsh home range  =  27.81 ± 6.3 ha). More than 40% of male and 18% of female home ranges had two discrete core areas and, in most instances, each core area corresponded to a separate lunar cycle. We suggest that differences in mating strategies, densities, and adaptation to nesting in tidal marshes explain the larger home range estimates for male Nelson's Sparrows. Female and male Nelson's Sparrows' home ranges had more Spartina alterniflora cover and female Saltmarsh Sparrows' home ranges had greater Juncus gerardii cover than random locations. Home ranges of female Saltmarsh Sparrows had less Spartina alterniflora cover and more Juncus gerardii cover than female Nelson's Sparrows. We did not detect any differences in vegetation variables between male Saltmarsh and male Nelson's sparrow home ranges.

Perceived similarity in appearance of eggs of the Brown-headed Cowbird (Molothrus ater) and several grassland passerine hosts has been suggested to represent a form of generalized mimicry evolved to impede egg discrimination. We tested this hypothesis by quantitatively comparing four parameters (ground color, maculation color, distribution of maculation, and maculation density) among cowbird eggs and those of six grassland passerines known to preferentially accept cowbird eggs over non-mimetic blue eggs. Cowbird eggs did not significantly differ in three of four parameters (mean ground color, and color and density of maculation) from the average grassland passerine egg measured for this community, in southern Saskatchewan, when all grassland passerine eggs were pooled. Cowbird eggs sufficiently overlapped grassland passerine eggs in these three parameters that 88% of cowbird eggs measured were statistically indistinguishable from among all grassland passerine eggs. The frequency at which cowbird eggs were misclassified as eggs of each grassland passerine ranged from 8 to 48%, which suggests that a single cowbird egg is capable of mimicking the eggs of more than one species. These results support the hypothesis that cowbirds have evolved a generalized egg appearance that mimics the eggs of multiple grassland passerine hosts within a single community.

We document the molt sequence of flight feathers in Turkey Vultures (Cathartes aura) based on studies of captive and wild birds, and examination of museum specimens. We found an unusual pattern of primary replacement, which appears to be a modified form of Staffelmauser, or stepwise wing molt. A Staffelmauser-like strategy for replacement of the secondaries is also described. These patterns of feather replacement appear to be adaptations to maintain flying performance while replacing all primaries and most secondaries during each molt. To what extent molt patterns in Turkey Vultures reflect convergent adaptation for flight, rather than ancestral characters useful for phylogenetic studies, remains unknown.

We report the first observations of cooperative polyandry in the Red-footed Booby (Sula sula), a trio that remained stable over at least 4 consecutive years. Both males were heterosexual; neither was dominant. One male was more sexually active, but mounting activity suggested shared paternity over the years. Trio males, compared to monogamous males, invested more in pair bond maintenance activity which possibly assisted in maintaining a stable breeding unit. Trio members, like monogamous adults, shared breeding duties evenly, reducing the total investment for each trio member relative to that of monogamous adults. The extra foraging effort of the trio enabled similar provisioning rates in good and bad years. We suggest trio formation improved female lifetime reproductive success due to enhanced nest, egg, and chick care; maintained stable food provisioning rates despite highly heterogeneous foraging conditions; and increased male survivorship due to sharing of breeding duties. Red-footed Booby trio formation is probably an “opportunistic deviation” from normal monogamy which is favored by differential costs and benefits to males and females.

We report evidence of egg-laying in northern Florida by the Shiny Cowbird (Molothrus bonariensis). Examination of the ovary and oviduct of a female trapped in Alachua County, Florida in late June 2006 revealed ovulation and recent passing of eggs. Two other Shiny Cowbird females captured in late May and early June had convoluted oviducts but showed no other signs of recent egg-laying. These three specimens add to the few female Shiny Cowbirds captured in North America. Our observations represent further evidence that Shiny Cowbirds likely breed in North America and additional evidence of breeding outside of southern Florida.

The Smooth-billed Ani (Crotophaga ani) is a plural-breeding, joint-nesting species that engages in both cooperation and reproductive competition. We report circumstantial evidence for infanticide of chicks by adults that joined a group after completion of the communal clutch. We provide evidence that some of the group adults captured after the infanticide were unrelated to any of the chicks and may have acted to increase chances of renesting.

Air speed of Red-necked Grebes (Podiceps grisegena), migrating in “no wind” conditions along a 2.64-km path along Lake Superior, Michigan in fall averaged 61.5 km/hr. Speed increased significantly using tail winds adjusted for wind vectors as the migration season advanced: 68 km/hr in August, 70.1 km/hr in September, and 78.7 km/hr in October. Horned Grebes (P. auritus) averaged 55.5 km/hr with no winds and, with tail winds, increased from 63.5 km/hr in September to 71.5 km/hr in October. Whether the increases indicate that late fall migrants are time constrained to complete their movement to wintering areas rapidly, or are a consequence of having to fly faster because of larger body mass at that season, remain to be fully explored. We also present flight speeds of 10 additional species of waterbirds migrating along the same path.

Birds in hyper-arid environments have acute problems of energy and water balance, and thermoregulate both physiologically and behaviorally. I report on European Bee-eaters (Merops apiaster) engaged in a previously unreported thermoregulatory behavior of diving into the sea and in salt ponds with high levels of salinity. This behavior may also explain the previously reported, but unexplained, finding of bee-eaters inside a tiger shark (Galeocerdo cuvier) in the Red Sea. These observations should instigate future experiments on the subject of selective use of salt water for evaporative cooling and thermoregulatory behavior by desert birds.

The Chuck-will's-widow (Caprimulgus carolinensis) in the Bahama Islands has been regarded as a rare to uncommon winter visitor. We conducted breeding season surveys on the three largest northern islands (North Andros, Grand Bahama, and Great Abaco) to examine the status of this species. We encountered singing birds on most survey routes on all three islands, suggesting that sizeable breeding populations are widespread in the northern Bahamas with an aggregate estimate of 500–1,000 pairs. Our density estimates were somewhat less than those from the primary range in the United States, suggesting either a lower carrying capacity in the Bahama Islands or recently established populations that have yet to reach carrying capacity.

Yellow Rails (Coturnicops noveboracensis) were recently discovered to migrate through southeastern Oklahoma in small numbers during fall with a few records into December and a single record in January. We made seven trips (3 in Nov 2008 and 1/month from Dec 2008 through Mar 2009) to Red Slough Wildlife Management Area in McCurtain County (Oklahoma) to catch and band Yellow Rails. Twenty-five Yellow Rails were banded and birds were observed during each month. Rails were encountered in areas dominated by Sporobolus spp. averaging 44 cm in height in areas with 4 cm or less of standing water. Yellow Rails appear to overwinter in small numbers in McCurtain County, Oklahoma ∼300 km north of the Gulf Coast.

We describe the nest sites, nests, eggs, and incubation and provisioning behavior of the endemic Giant Laughingthrush (Garrulax maximus) in a coniferous forest (2,850–2,950 m asl) at Lianhuashan, southern Gansu, central China. We found seven shallow bowl-shaped nests in Picea-Abies trees, 4.0 ± 1.5 m (x¯ ± SD, n  =  7) above the ground during May and June 2003, 2007, and 2008. Clutch size was 2.2 ± 0.4 unspotted blue eggs (2–3, n  =  6) of which 1.4 ± 0.5 nestlings hatched (1–2, n  =  7), and 1.0 ± 1.0 young fledged (0–2, n  =  7). Three nests failed, possibly due to predation or abandonment during prolonged rainfall. Both males and females incubated clutches; nest attentiveness during the day decreased from 92.6 ± 0.9% before hatching to 59.4 ± 1.5% during days 3–7 of the nestling period. Both parents fed the nestlings (1.0 ± 1.0 times/hr) and consumed the feces (0.3 ± 0.5 times/hr) during the 7–15 days after hatching

The Jocotoco Antpitta (Grallaria ridgelyi) is an endangered and poorly studied inhabitant of montane bamboo (Chusquea spp.) thickets of extreme southeastern Ecuador. There is nothing known of the breeding biology of Jocotoco Antpitta apart from a single record of a dependent juvenile, and we describe a nest of this species for the first time. The nest was a bulky cup composed primarily of dead plant materials and firmly supported by a large clump of epiphytes on the side of a dead trunk. The single nestling was provisioned at a rate of 1.96 feedings/hr during the final 5 days prior to fledging. Two adults brought food to the nestling, often delivering prey from a nearby worm-feeding station created by the Jocotoco Foundation. The pair we studied may breed twice a year, but this may have been facilitated by their proximity to the artificial feeder.

We studied the breeding ecology of the Grey-backed Shrike (Lanius tephronotus) in alpine shrub habitats in south Tibet. Shrikes nested between late May and early July at elevations of 4,010–4,540 m with a delay in nesting time with increased elevation. Nests were built mostly in bushes (83%), 0.7–2.1 m above ground. Clutch size averaged (± SD) 4.12 ± 0.67, range  =  3–5 eggs and was smaller for pairs that nested later at higher elevations. Incubation by females began before clutch competition and lasted 15–18 days. Nestlings were cared for by both parents for 14–15 days. Breeding success, considered as the number of nest attempts that fledged at least one young, was 45.8%. Shrikes nesting in alpine habitats, compared with their lowland congeners, experienced shorter breeding seasons, produced fewer broods, smaller clutches, and larger eggs. They followed a life history strategy that allowed them to compensate for reduced annual fecundity under harsh conditions.

Two mixed pairs of towhees were found in irrigated desert yards near Tucson, Arizona. The first known towhee F₁ hybrids, from a female Pipilo aberti (Abert's Towhee) and male P. fuscus (Canyon Towhee) were studied from winter of 1998–1999 through summer 2000. This mixed pair raised at least eight young in three broods during the two breeding seasons. Young were so similar to P. fuscus that, if seen outside this context, they would probably not be identified as hybrids. A second mixed pair, also near Tucson, suggests that hybridization between P. aberti and P. fuscus may be more common than originally thought. Lack of previously reported hybridization between P. aberti and P. fuscus may be either due to internal or external isolating mechanisms, limited survival and longevity, or human failure to recognize hybrids.

I observed a Red-winged Blackbird (Agelaius phoeniceus) nest in southcentral Wisconsin, USA that received a Yellow-billed Cuckoo (Coccyzus americanus) egg. The cuckoo egg was laid after the blackbird clutch was complete and the female had begun incubation. The parasitic egg was considerably different in size and color, but was accepted by the female Red-winged Blackbird. The female, but not the male, also cared for the nestling, which was strikingly different in plumage, gape markings, and begging behavior, and which grew despite its 3–4 day hatching delay relative to its nest mates. Rapid development and exaggerated begging behavior of the Yellow-billed Cuckoo nestling may enable a parasitic cuckoo nestling to compete successfully with host nestlings for food.