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We examined factors hypothesized to influence Ruffed Grouse (Bonasa umbellus) population cycles by evaluating 13 a priori models that represented correlations between spring counts of male Ruffed Grouse drumming displays and these factors. We used AICc to rank the relative ability of these models to fit the data and used variance components analysis to assess the amount of temporal process variation in Ruffed Grouse spring counts explained by the best model. A hypothesis representing an interaction between winter precipitation and winter temperature was the top-ranked model. This model indicated that increased precipitation during cold winters (soft snow cover for roosting) was correlated with higher grouse population indices, but that increased precipitation during warm winters (snow crust effect) was correlated with lower spring counts. The highest ranked model (AICc weight = 0.45), explained only 17% of the temporal process variation. The number of migrating Northern Goshawks (Accipiter gentilis), which has been correlated with grouse cycles in previous studies, does not adequately explain, by itself, the variation in annual population indices of Ruffed Grouse. Other factors not considered in our analysis, such as endogenous mechanisms, parasites, or interactions among factors may also be important, which suggest that mechanisms mediating the Ruffed Grouse cycle still require investigation.
Many species of trogons (Trogoniformes: Trogonidae) gather in mixed-gender calling assemblages during the breeding season. These assemblages have been compared to leks and are usually assumed to function in mate choice; however, no field data exist to support this hypothesis. I present five non-mutually exclusive hypotheses for the function of mixed-gender calling assemblages and test the predictions using field data from Black-headed Trogons (Trogon melanocephalus) in a lowland dry forest in Costa Rica. Adult trogons gathered in mobile assemblages of 3–12 individuals that called frequently and chased one another from perch to perch while moving through the forest. Groups formed at sunrise throughout all stages of the breeding cycle and were not significantly male-biased. Both breeding and non-breeding individuals participated in assemblages, and copulations were not observed in assemblages. Prey capture rates of individuals foraging in groups did not differ from those foraging alone. Males called and chased other individuals more often than did females; however, males chased females and other males at equal rates. Assemblages of trogons frequently prospected (investigated potential nest sites and active nests of conspecifics). These data suggest that communal assemblages of calling trogons do not function solely in social mate choice, nor do they enhance foraging efficiency. They may have a role in maintenance of territorial boundaries and selection of future nest sites.
I examined song variation within and among 23 individual Buff-breasted Flycatchers (Empidonax fulvifrons) recorded in the Chiricahua and Huachuca mountains of Arizona in 1999. I recorded two distinct song types from each individual during intense pre-dawn singing. I used both spectrographic cross correlation (SPCC) of entire songs and discriminant function analysis (DFA) of temporal and frequency measurements to examine whether songs were individually distinctive, and whether songs differed between the two localities. Similarity values of pairs of songs from SPCC were significantly greater for within-male than for between-male comparisons for both song types. Mean similarity values for the two song types did not overlap between these comparison categories. Similarity values between songs of pairs of males from the same mountain range were not greater than for comparisons between pairs of males from different ranges. All temporal and frequency measures for both song types varied significantly more among than within individuals. DFA of principal component scores derived from these measures assigned 85% of Type 1 and 86% of Type 2 songs to the correct individual. Only three frequency variables measured from Type 1 songs differed significantly between birds from the two mountain ranges. DFA assigned only 61% of songs of either type to the correct mountain range, not significantly greater than expected by chance. Thus, both techniques demonstrate significant individual distinctiveness in songs of this species, and neither suggests any geographic structuring of song variation between the two mountain ranges. However, SPCC is considerably more efficient and has greater potential to assign unknown recordings to known individuals correctly, and to detect recordings of “new” individuals not included in the reference sample.
We investigated the phylogenetic relationship and differences in the song structure between the Philippine Bush Warbler (Cettia seebohmi) and the Japanese Bush Warbler (C. diphone). We compared complete sequences of the mitochondrial cyt-b gene of C. seebohmi to those of other Cettia taxa from GenBank and found C. seebohmi formed a monophyletic group with C. haddeni and C. diphone. The phylogenetic tree also suggests that C. seebohmi is more closely related to C. haddeni than to C. diphone although this was not strongly supported due to the low bootstrap values. The estimated nucleotide differences between C. seebohmi and C. haddeni (4.37%), and between C. seebohmi and C. diphone (3.87–4.37%) were larger than the inter-subspecific difference between C. diphone borealis and C. d. cantans (2.44%). Cettia seebohmi, C. haddeni, and C. diphone diverged prior to the subspecies divergences of C. diphone. The basic structure of songs was similar in C. seebohmi and C. diphone; all songs consisted of pure monotone whistles followed by variably modulated warbles. However, sonagraphic parameters showed statistically significant differences between species. It is reasonable to regard C. seebohmi and C. diphone as separate species.
The southeastern Yucatan Peninsula hosts high numbers of transient Nearctic-Neotropic migrants during autumn migration, but the importance of this region during migratory stopover has not been addressed. We studied autumn stopover body mass gains among passerine migrants in tropical lowland forest 20 km inland from the Gulf of Honduras. Most individuals captured had some subcutaneous fat. Ten of 15 taxa with sufficient sample sizes had significant positive diel (24 hr) gains in a body condition index. Estimates of net mass gains in these 10 taxa suggested they all were depositing fat; average individuals in four of these taxa were depositing sufficient fuel to undertake an entire night of migration after only 1 day of fattening: Empidonax spp., Red-eyed Vireo (Vireo olivaceus), Gray Catbird (Dumetella carolinensis), and Northern Waterthrush (Seiurus noveboracensis). Two (Wood Thrush [Hylocichla mustelina] and Common Yellowthroat [Geothlypis trichas]) of the four species apparently not gaining mass at the study site migrate late in the season and occurred only after Hurricane Iris severely altered the habitat. Four other species (Gray Catbird, Magnolia Warbler [Dendroica magnolia], American Redstart [Setophaga ruticilla], and Indigo Bunting [Passerina cyanea]) had significant gains in mass after the hurricane. These data demonstrate the importance of the region as an autumn stopover site for some species and suggest that stopover areas farther north are also important to migrants passing through the southeastern part of the Yucatan Peninsula.
Migratory birds were surveyed at stopover sites in New Orleans, Louisiana, during seven spring and fall seasons in relation to weather conditions. Weather was classified into four synoptic scenarios distinguished primarily by positions of fronts, wind directions, and pressure characteristics. Overall numbers of migrants in spring were more numerous during the synoptic scenarios in which a cold front was about to arrive (Frontal Gulf Return) or had already passed (Post Frontal), than when airflow was off the Gulf or from the east (Coastal Return, which often preceded frontal passage). Counts of White-eyed (Vireo griseus) and Red-eyed vireos (V. olivaceus), Indigo Buntings (Passerina cyanea), and thrushes (Hylocichla and Catharus combined) showed differences among weather scenarios, mostly with high counts under Post Frontal conditions and/or low counts under Coastal Return. Post Frontal values were higher in fall than Coastal Return for overall migrants, Common Yellowthroats (Geothlypis trichas), and Indigo Buntings. However, four individual species failed to show any variation with weather. Counts after cold front passages in both spring and fall were higher than those preceding the fronts for all migrants combined.
We measured rates of mass change of eight species of migratory passerines in a New York City park during three consecutive spring and autumn migrations to evaluate the quality of an urban habitat as a stopover site. We also examined seasonal differences in body condition. Linear regressions of a condition index on time of day detected significant hourly mass gain by Magnolia Warbler (Dendroica magnolia), Black-throated Blue Warbler (D. caerulescens), Ovenbird (Seiurus aurocapilla), and Northern Waterthrush (S. noveboracensis) during spring, and Common Yellowthroat (Geothlypis trichas) during autumn. Swainson's Thrush (Catharus ustulatus) showed significant mass loss during autumn. Significant spring mass gain rates ranged from 0.99 to 2.46% of mean body mass/hr. Common Yellowthroat gained 1.28% of mean body mass/hr during autumn. Most species were heavier and fatter in spring than autumn. The significant mass gain rates were comparable to those in similar studies in more pristine areas. Our results suggest the urban stopover site we examined is a place where migrants can sufficiently replenish energy stores. This highlights the importance of conserving and properly managing remaining green spaces in urban areas along major migratory bird flyways.
We used satellite telemetry locations accurate within 1 km to identify migration routes and stopover sites of 54 migratory sub-adult Bald Eagles (Haliaeetus leucocephalus) hatched in Florida from 1997 to 2001. We measured number of days traveled during migration, path of migration, stopover time and locations, and distance traveled to and from winter and summer areas for each eagle (1–5 years old). Eagles used both Coastal Plain (n = 24) and Appalachian Mountain (n = 26) routes on their first migration north. Mountain migrants traveled farther (x̄ = 2,112 km; 95% CI: 1,815–2,410) than coastal migrants (x̄ = 1,397 km; 95% CI: 1,087–1,706). Eagles changed between migration routes less often on northbound and southbound movements as they matured (χ2 = 13.22, df = 2, P < 0.001). One-year-old eagles changed routes between yearly spring and fall migrations 57% of the time, 2-year-olds 30%, and 3–5-year-olds changed only 17% of the time. About half (n = 25, 46%) used stopovers during migration and stayed 6–31 days (x̄ = 14.8 days; 95% CI: 12.8–16.8). We recommend that migratory stopover site locations be added to GIS data bases for improving conservation of Bald Eagles in the eastern United States.
Habitat loss, introduced predators, and hybridization with feral Mallards (Anas platyrhynchos) continue to threaten the existence of the endangered Hawaiian Duck or Koloa maoli (A. wyvilliana). Protection and management of core breeding areas is a recovery objective, but lack of quantitative information on the species' habitat needs hinders recovery efforts. We conducted bi-monthly surveys of 48 wetlands on private lands on the Island of Hawai`i from March 2002 to June 2003. We compared Koloa use between seasons, wetland types, and study regions and modeled how use varied with 14 site and landscape variables. Koloa occupied 54% of the surveyed wetlands; use was higher on wetlands enhanced or created for Koloa primarily through the USDA's Wetlands Reserve Program (WRP) than on ponds created for agriculture (81 vs. 41%) and on wetlands in the Kohala than in the Mauna Kea region (93 vs. 38%). Koloa were more likely to use wetlands farther (>600 m) from houses, larger (>0.23 ha) wetlands, and those surrounded by more wetlands area (>1 ha). Our results (1) indicate WRP wetlands provide suitable habitat and (2) support wetlands enhancement or creation far from human disturbance. Habitat improvements combined with feral Mallard control may reduce extinction threats to Koloa.
We investigated environmental variables linked to presence of Barrow's Goldeneye (Bucephala islandica) pairs from the eastern North American population on 412 lakes of the Sainte-Marguerite River watershed, Québec, Canada. We analysed habitat relationships at two spatial scales (i.e., considering all lakes surveyed and high elevation lakes only) and predetermined the high elevation lakes as those including 90% of Barrow's Goldeneye occurrences. Barrow's Goldeneye were found on 59 lakes, all of which were ≥490 m elevation (maximum = 822 m) with 90% at ≥610 m. Six variables tested using multivariate logistic regressions contributed to explain the occurrence of goldeneyes. Four were significant (P < 0.10) in both the complete and the high elevation data sets: nest boxes ( ) and brook trout (Salvelinus fontinalis) (−) occurrences, altitude ( ), and the interaction between altitude and mean slope ( ). The models explained only a small proportion of Barrow's Goldeneye occurrence for both data sets (R2 = 0.27 and 0.23, respectively). The negative relationship between Barrow's Goldeneye and brook trout occurrences, and the positive relationship with altitude probably reflect a positive relationship between goldeneye and highly productive aquatic ecosystems. Barrow's Goldeneye from eastern North America primarily use high altitudinal, productive lakes during the breeding season, which emphasizes the importance of fishless lakes for that population at risk.
We surveyed 366 historical and potential nesting sites for Black Swifts (Cypseloides niger) from 1997 to 2005 in the Southern Rocky Mountains, evaluated their suitability for nesting, and searched for evidence of occupancy. Our surveys located 70 previously undocumented occupied sites, increasing the inventory of sites in the region from 33 to 103. Our results provide a preliminary estimate of Black Swift population size. Comparison of observed colony sizes with those reported in earlier studies suggests little or no change in population levels over the past 50 years. We rated each nest site on conformance to characteristics described in earlier studies. Analysis of 291 site evaluations support a priori assumptions that increasing stream flow, number of potential nest platforms, amount of available moss, shading of potential nest niches, topographic relief of surrounding terrain, and ease of aerial access to potential nest niches contributed to a higher probability the site would be occupied by Black Swifts.
Vermilion Flycatchers (Pyrocephalus rubinus) were documented to reuse their nests within a single breeding season in south Texas. I recorded a consistent, low frequency (12%, n = 250 clutches) of nest reuse during each of four seasons. Nest survival was greater (P < 0.001) for reused nests than for newly constructed nests and the abundance of ectoparasites was low overall for both types of nests. The main advantage for Vermilion Flycatchers reusing nests was greater nesting success as nest reuse was associated with reduced nest predation. Nest reuse also increased time available for nesting attempts as a flycatcher would save 8 days (9%) (during three attempts) of the time typically available for nesting in south Texas. Reported nest reuse was common (>25% of a family's members) among 5 families of passerines. Aspects of the life histories of these groups support hypotheses for the observed nest reuse behavior among Vermilion Flycatchers.
We provide substantial new information on the breeding biology of the Rusty-breasted Antpitta (Grallaricula ferrugineipectus ferrugineipectus) from 40 nests during four consecutive breeding seasons at Yacambú National Park in Venezuela. Vocalizations are quite variable in G. ferrugineipectus. Nesting activity peaked in April when laying began for half of all nests monitored. The date of nest initiation pattern suggests this species is single-brooded. Both parents incubate and the percent of time they incubate is high (87–99%) throughout the incubation period. The incubation period averaged (± SE) 17.0 ± 0.12 days, while the nestling period averaged 13.37 ± 0.37 days. G. f. ferrugineipectus has the shortest developmental time described for its genus. Time spent brooding nestlings decreased as nestlings grew, but was still greater at pin feather break day than observed in north temperate species. The growth rate constant based on mass (k = 0.41) and tarsus length (k = 0.24) was lower than the k for north temperate species of similar adult mass. All nesting mortality was caused by predation and overall daily survival rate (± SE) was relatively low (0.94 ± 0.01) yielding an estimated 15% nest success.
We studied the diet and foraging ecology of a community of six psittacines in western Costa Rica. All had a varied diet with clear seasonal changes in preferred food items, mostly due to changes in plant phenology. There was a significant relationship between parrot mass and food types: larger-bodied parrots consumed more seeds and smaller-bodied parakeets consumed more fruit pulp. Leaves, bark, and lichen were also consumed by most psittacines. Most parrots consumed more plant species in the dry season when food availability was at its peak. Levins' niche breath showed varying levels of diet specialization among species and, for some species, variation among seasons. There was less similarity in seasonal psittacine diets when compared to overall diets. Scarlet Macaws (Ara macao) under study were captive raised and released which may have contributed to their narrow diet breadth as they may have lacked the knowledge or experience to exploit additional food sources. Non-native and cultivated species comprised 76% of the diet of Scarlet Macaws, and averaged 28% for all other species. This suggests that foraging parrots may have increased conflicts with humans as landscapes become increasingly modified. Forest restoration strategies should augment the abundance of food species consumed when overall food supply is at its annual low.
The decline of Golden-winged Warblers (Vermivora chrysoptera) has been attributed in part to hybridization with a sister species, the Blue-winged Warbler (V. pinus), which lacks the black throat patch typical of the Golden-winged Warbler. Understanding the signal function of male plumage ornaments in Golden-winged Warblers may provide insight into the mechanisms driving hybridization. If Golden-winged Warbler males use the black throat patch for interspecific signaling, Blue-winged Warblers or hybrids may be leading hybridization between the species. We examined the signal function of the melanin-based throat patch in a population of Golden-winged Warblers on the edge of the hybrid zone. Males with increased ultra violet chroma in their throat patches were older and their mates had significantly earlier first egg dates. This suggests the black throat patch of Golden-winged Warblers may be an age-related indicator of quality. Female Golden-winged Warblers should not mate preferentially with males which lack the black throat patch if it functions as an indicator of age and or male quality.
House Finches (Carpodacus mexicanus) in North America are a commonly-studied species, but basic aspects of their life history remain poorly understood. I banded and observed marked House Finches at a backyard feeding site in a suburban neighborhood in Atlanta, Georgia from August 2002 through July 2004 to address how age, gender, mycoplasmal conjunctivitis, and time of year affected fidelity of individual House Finches to this site. Of 386 House Finches banded, I recaptured 77 and recorded 1,210 reobservations. More than half (55%) of all birds banded were not seen again and, of those that were, almost half (44%) were seen for less than 2 months. A House Finch's age, gender, and month of capture significantly affected how many times it was subsequently encountered (recaptured or reobserved), but not the duration of time it spent at the site of banding. Young birds (HYs) were encountered more often than adults (AHYs), and females more than males. Young birds with mycoplasmal conjunctivitis were encountered less often than those without, but this was not true for adults. These data indicate high site fidelity of adults during the breeding season and low site fidelity of juveniles early in the summer that becomes higher in late summer. Most birds captured in fall were encountered for up to 3 months. These results are discussed in relation to previous studies and their implications for transmission of Mycoplasma gallisepticum among House Finches.
Caspian Tern (Sterna caspia) plumage characteristics are sexually monochromatic and gender cannot easily be distinguished in the field without extensive behavioral observations. We assessed sexual size dimorphism and developed a discriminant function to assign gender in Caspian Terns based on external morphology. We collected and measured Caspian Terns in San Francisco Bay, California, and confirmed their gender based on necropsy and genetic analysis. Of the eight morphological measurements we examined, only bill depth at the gonys and head plus bill length differed between males and females with males being larger than females. A discriminant function using both bill depth at the gonys and head plus bill length accurately assigned gender of 83% of terns for which gender was known. We improved the accuracy of our discriminant function to 90% by excluding individuals that had less than a 75% posterior probability of correctly being assigned to gender. Caspian Terns showed little sexual size dimorphism in many morphometrics, but our results indicate they can be reliably assigned to gender in the field using two morphological measurements.
We investigated the effects of urban noise on auditory surveys of White-winged Doves (Zenaida asiatica) in two major cities in Texas. We conducted auditory point counts throughout the morning in San Antonio (n = 6) and Austin (n = 10) during week days (when traffic noise is higher) and weekends. We categorized survey points as near or far from roads (<0.8 and >0.8 km, respectively) for comparison. We documented no difference in density estimates in Austin between week days (46 ± 10 pairs/ha) and weekends (52 ± 10 pairs/ha; P = 0.23); however, weekend estimates were consistently higher throughout the morning. Weekend density estimates in San Antonio were higher after 0620 hrs (P < 0.04), the time coinciding with beginning of the morning commute during week days in this city. We documented that weekend estimates (45 ± 5 pairs/ha) were higher than week day estimates (33 ± 5 pairs/ha) for points near roads (within 0.8 km; P = 0.02) but not for points far from roads (P = 0.16). Our results indicate that traffic noise can bias auditory surveys. Survey methods that account for probability of detection should be used to correct for potential noise bias.
Body size measurements from freshly collected birds and dried museum specimens were used to evaluate specimen shrinkage in Cinnamon Teal (Anas cyanoptera). Six of seven body measurements of female Cinnamon Teal differed significantly after specimen drying, whereas five of seven male body measurements differed. The largest amount of shrinkage was in bill height, bill width, and tarsus length. Bill length at nares showed no significant shrinkage suggesting it is a more conservative measurement than exposed culmen and, therefore, a more reliable method for accurately measuring bill length. Correction values for body size measurements are reported for future waterfowl studies combining measurements of both live birds and museum specimens.
The Coastal Plain Swamp Sparrow (Melospiza georgiana nigrescens) is morphologically distinct, restricted to a narrowly-defined habitat type, and geographically isolated within the mid-Atlantic Coastal Plain. The breeding range has been considered to extend from the Nanticoke River in Maryland north to the Hudson River. We report a previously undocumented population near Warsaw, Virginia that extends the known range south and west into a region of the Chesapeake Bay with extensive tidal fresh and brackish marshes consistent with the habitat requirements of this form, but for which there has been no documented breeding. A broader investigation of occurrence within appropriate habitat seems warranted given the small global population size and uncertain status within the southern portion of its range.
Polyandry occurs when females form social bonds and gain simultaneous parental care from multiple male mates. It is thought to be rare in birds and to occur more often in territorial species when the Operational Sex Ratio (OSR; ratio of mature males to females) exceeds one. We asked if variation in the OSR affected the rate of polyandry in Song Sparrows (Melospiza melodia) over 30 years on Mandarte Island, British Columbia, Canada. We found no correlation between OSR and polyandry (Rs = 0.04, df = 28, P = 0.86), but positive correlations between OSR and percent females with more than one social mate (Rs = 0.44, df = 28, P = 0.01), and percent females sharing a territory with a replacement male and her dependent young (Rs = 0.46, df = 28, P = 0.009). We suggest that polyandry in Song Sparrows is limited by the intolerance of territorial males towards intruders, but that it occurs when females occupy the territories of two or more males and gain their simultaneous care for the dependent young of a single brood as a consequence.
The Little Greenbul (Andropadus virens) is a common African forest bird that is thought to form monogamous pair bonds. In March 2007, I observed a male hanging below a presumed female perched on a branch, apparently inspecting her cloaca and clinging to her when she flew from that branch, while singing throughout. This apparent mate guarding behavior suggests that extra-pair fertilizations may occur in this species.
On 28 April 2006 in Ohio and again on 19 May 2006 in North Carolina, I observed and, on the April occasion, recorded a Yellow-throated Warbler (Dendroica dominica) singing a type B song. A sound spectrogram of this rare song is compared with the more common type A song of this species. I present evidence that my recording is a type B song and speculate on the rare condition and function of this song.
We studied substrate composition and vegetation cover at Piping Plover (Charadrius melodus) nests and paired random plots on New York beaches that had been widened by renourishment (deposition of dredged sand). Most nests (59.4%, n = 32) were in unvegetated plots, mean ± SE vegetative cover around nests was 7.5 ± 1.7%, and all plovers nested in <47% cover. Most nests (59.4%) were on pure sand and mean coarse grain cover (pebble and cobble-sized objects) on nest plots was 9.1 ± 2.6%. Nest plots were more likely to be vegetated than paired random plots. Coarse substrate also was of high relative importance in distinguishing nests and random plots. Beach management projects can reduce sparse vegetation and coarse substrate, which may affect Piping Plover nest site selection.
We observed a male Black-capped Vireo (Vireo atricapilla) exhibiting nest site selection in east-central Texas. The paired male was observed to deconstruct the nest the female was assembling. To our knowledge, male nest site selection has not been observed and reported in the literature for vireos.
Black-throated Green Warblers (Dendroica virens) typically place their nests within the dense foliage of a limb or in a branch fork against the trunk of a living conifer. I report four unusual nests from Algonquin Provincial Park, Ontario, Canada: three in feeding cavities of Pileated Woodpecker (Dryocopus pileatus) in snags (i.e., dead trees), and one in a sugar maple borer (Glycobius speciosus, Coleoptera: Cerambycidae) scar in a tree of declining health. These data are the first documentation of this species nesting within cavities and enhance our understanding of the importance of snags and trees in declining health for wildlife.
Information on the breeding behavior of the Red-ruffed Fruitcrow (Pyroderus scutatus) is scarce and restricted to the subspecies P. s. granadensis and P. s. orenocensis. We found the first nest of the nominate subspecies (P. s. scutatus) in an Atlantic Forest area in southeastern Brazil on 28 November 2004. The nest contained two nestlings and was built on a horizontal fork, 16.7 m above ground. It was cup-shaped with a substantial base composed of twigs: outside diameter 38 cm, cup diameter 16.5 cm, outside height 11.3 cm, and inside height 5 cm. The nestlings were thickly covered with brownish down. Only one unknown gender adult visited the nest. Although locally endangered, the breeding cycle of this species remains poorly known.
We observed an adult male Hawai‘i ‘Amakihi (Hemignathus virens) repeatedly feed a fledgling Palila (Loxioides bailleui). We observed 16– 19 food provisions during 14 hrs of observation between 21 and 29 June 2006. The presumed biological parents were frequently seen nearby, but adult Palila were not observed feeding the fledgling.
We describe an adoption event by a female Eastern Bluebird (Sialia sialis) and suggest a mechanism by which adoption could be adaptive. The foster female adopted three young and we were able to quantify two measures of parental care (nestling provisioning and nest defense). The foster female successfully reproduced with the father of the young in the same location later in the breeding season. The adopting female may be increasing her fitness by gaining future reproduction with a fertile mate at a productive nest box through parental care for young that are not related.
Intraspecific killing without cannibalism is rare in birds. I report an observation of an adult Pacific Reef Egret (Egretta sacra) killing an adult conspecific at One Tree Island, Great Barrier Reef, Australia. The motivation and context for the killing were not apparent. To the best of my knowledge, this is the first report of intraspecific killing in Pacific Reef Egrets.