Diet of Bald Eagles (Haliaeetus leucocephalus) in the Florida Bay estuary was determined from prey remains from nest sites and used to evaluate differences between two time periods, the 1972 and 1973 breeding seasons compared with 2009 and 2010. Between these two time periods, Florida Bay underwent a well-documented series of ecological changes beginning in the late 1980s, which significantly altered the ecosystem. To examine the hypothesis that ecological changes may have shifted Bald Eagle diets, we compared 571 remains (30 species) collected in 1972/1973 from 21 nest sites, to 419 remains (22 species) collected sites in 2009/2010 from 11 nest sites. Fish made up the majority of prey in 1972/1973 and 2009/2010 (80.7% and 69.5% by number, respectively) and birds were second (15.8% and 29.1%). Hardhead catfish (Arius felis) skulls made up the majority of individual prey remains in both time periods (55% and 54%). Bald Eagles also ate significantly larger catfish in the 1972/1973 seasons, as the mean total skull length was 10% greater and estimated biomass was 35.7% greater. There was no difference in overall prey diversity between the two time periods; however, analysis of similarities showed prey composition differed. Mullet (Mugilidae), jack (Carangidae), Double-crested Cormorant (Phalacrocorax auritus), and Red-breasted Merganser (Mergus serrator) were the species that contributed most to the dissimilarities between time periods. We suggest that Florida Bay's ecological and prey community changes during this time period influenced Bald Eagle diets.

The little-known Eurasian Sparrowhawk of Macaronesia (Accipiter nisus granti), also named as the Macaronesian sparrowhawk, is endemic to Madeira Island and the Canary Islands (North Atlantic Ocean) and has the smallest area of distribution of the sparrowhawk subspecies. We studied the breeding biology of the Macaronesian sparrowhawk for the first time on Madeira Island, Portugal. Specifically, we described nests, tree nests, nest sites, and nesting territories, and we estimated incubation, hatching and fledging dates. Moreover, we evaluated the influence of altitude on the date of the initiation of breeding and measured the number of fledglings and the factors influencing this parameter. Most nesting territories (88.6%) were located in forest patches where valleys with watercourses were present. Breeding success (73.2% ± 0.1 SE, n = 18) and the mean number of young fledged per nest with eggs (2.27 ± 0.04) are lower than the values for the Canary Islands. Altitude influenced the date of the initiation of breeding, with pairs in lowlands (<700 masl) initiating breeding earlier. However, pairs breeding earlier did not have higher reproductive rate than those breeding later. The number of fledglings per nest with eggs in mixed habitats was higher than in exotic and Laurel forests. The main cause of breeding failure was forest cutting. We believe that if the forestry industry does not consider the nesting areas, as well as the breeding phenology of this subspecies, and forest fires are not prevented, then its population in Madeira may be reduced in the near future.

Raptor migration rarely involves long-distance movements across open oceans. One exception occurs along the East-Asian Oceanic Flyway. We collected migration data at two terrestrial hawkwatch sites along this flyway to better understand open-ocean movements along this largely overwater corridor. At the northern end of the Philippines, at Basco on the island of Batan, we recorded 7587 migratory raptors in autumn 2014. Near the southern end of the Philippines, at Cape San Agustin on the island of Mindanao, we recorded 27,399 raptors migrating in autumn 2012. Chinese Sparrowhawks (Accipiter soloensis) were the most common raptors observed, making up approximately 89% and 92% of total records for Basco and Cape San Agustin, respectively. The Grey-faced Buzzard (Butastur indicus) was the second most common raptor migrant, accounting for 8% of the total counts at both watch sites. The migration period was about 1–2 wk earlier at Basco, the more northerly site, than at Cape San Agustin. Overwater flights at Basco peaked in both the morning and late afternoon, whereas at Cape San Agustin there was only a morning peak. In general, the rate of migration passage at both sites was highest with clear skies when winds were blowing from the northwest. However, we observed interspecific differences in migration behavior at both sites, with Accipiters more likely to be observed with tailwinds and eastward winds, and Grey-faced Buzzards more likely observed with headwinds. These results help to characterize poorly known aspects of raptor biology and to identify potential migratory bottlenecks or key sites for raptor conservation in little-studied Philippine tropical ecosystems.

We evaluated the species composition, relative abundance, habitat use, and seasonal variability of raptor assemblages in the Flooding Pampas of Argentina, which represents the southeastern part of the biome known as the Rio de la Plata Grasslands. We conducted seasonal roadside surveys to detect raptors in modified and natural habitats over a 3-yr period from spring 2006 through autumn 2009. We classified raptor species according to their relative abundances and occurrence frequencies, and compared the assemblage composition among land-cover types (croplands, grazing fields, periurban areas, and grasslands) and seasons. The raptor assemblage in the Flooding Pampas comprised 16 species, representing approximately 43% of all raptor species in the biome. The Chimango Caracara (Milvago chimango) was the dominant species in all land-cover types and seasons. The Southern Caracara (Caracara plancus), American Kestrel (Falco sparverius), and Roadside Hawk (Rupornis magnirostris) were all abundant and very frequently observed species, whereas Burrowing Owl (Athene cunicularia), White-tailed Kite (Elanus leucurus), and Long-winged Harrier (Circus buffoni) were less abundant but recorded during most surveys. The remaining raptors (Aplomado Falcon [Falco femoralis], Cinereous Harrier [Circus cinereus], Short-eared Owl [Asio flammeus], Sharp-shinned Hawk [Accipiter striatus], and Snail Kite [Rostrhamus sociabilis]) were much less abundant in the study area. We also recorded four other raptor species (Variable Hawk [Geranoaetus polyosoma], Black-chested Buzzard-Eagle [G. melanoleucus], Striped Owl [Asio clamator], and Barn Owl [Tyto alba]), but only outside of the standard transect surveys. Species composition differed among land-cover types, but we detected no distinct overall seasonal patterns except that species diversity indices were lower in autumn and especially, spring. Milvago chimango was important to determine similarity in assemblage composition within land-cover types, but other less abundant species, such as C. plancus, A. cunicularia, and R. magnirostris, were more important to differentiate land-cover types based on raptor composition. Species diversity was highest in grazing fields and grasslands, and lowest in periurban areas. Our results suggest that although some raptor species appear to benefit from land-cover patterns in the study area, many other species may be threatened by the expansion of urban areas and agriculture in the Pampas region.

Installation of nest boxes for a declining raptor species, the American Kestrel (Falco sparverius), in agricultural areas may benefit both local kestrel conservation and management of prey species that cause damage to crops. Kestrels responded quickly to the installation of 18 new nest boxes in northwestern Michigan cherry (Prunus spp.) orchards between 2012 and 2013; they made nesting attempts (laid eggs) in 100% of boxes by 2015. In addition, kestrels that made nesting attempts in these boxes in 2013–2015 showed high reproductive rates: apparent nesting success was 91%, and mean number of fledglings per box with nesting attempts was 3.8. Also, kestrels were highly tolerant of both traditional monitoring techniques (opening the box) and newer camera technologies (a pole-mounted video camera and nest-box video cameras). Generalized linear modeling indicated that variables related to nest monitoring techniques and effort did not significantly affect daily survival rates for nests or brood size at fledging for successful nests; only hatching date had a small positive effect on brood size at fledging. These results suggest that orchard nest boxes have the potential to sustain or increase the breeding kestrel population in the region while increasing kestrel predation of crop-damaging prey in and around cherry orchards. This is promising for ongoing and future work with nest boxes in agricultural regions.

Red-shouldered Hawk (Buteo lineatus) eggs were examined to determine whether mass, eggshell thickness, and a thickness index corrected for egg shape and blowhole size changed as embryos developed. Four different stages of embryonic development (fresh, slight, large, and advanced) were described by the collector (C.F. Stone), or inferred from blowhole diameter measurements, for 286 Red-shouldered Hawk eggs collected in the late 1800s and early 1900s in central New York State. We examined changes in eggshell mass, thickness, and thickness index with linear mixed models with year of collection and clutch size specified as random variables. We also evaluated annual differences in eggshell characteristics with linear mixed models. There was an 8.8% decrease in eggshell mass between eggs with fresh and advanced embryos at the time of collection (F_3,242 = 3.4, P = 0.02). Eggshell thickness tended to decrease by 7.5% between eggs with fresh and advanced embryos, but the difference was not significant (F_3,119 = 2.06, P = 0.11). The thickness index also did not change due to stage of embryonic development. The year in which eggs were collected influenced eggshell mass (F_12,187 = 2.35, P = 0.008) and the thickness index (F_12,188 = 2.68, P = 0.002), but not thickness. This is the first study of eggs collected from wild raptors that demonstrates the magnitude of the effect embryonic development has on eggshell characteristics.