The avian alimentary tract has evolved into different histologic structures to accommodate the physical and chemical features of several food types and flight requirements. We compared the esophagus, proventriculus, and gizzard of the domestic fowl, Gallus gallus domesticus (GGD) and kestrels, Falco tinnunculus (FT) using immunohistochemistry and scanning electron microscopy with various stains and lectins [Dolichos biflorus agglutinin (DBA) and Ricinus communis agglutinin I (RCA120)], and α-smooth muscle actin (α-SMA). The esophagus of GGD demonstrated thickened epithelium, muscularis mucosae, and inner circular longitudinal tunica muscularis layers; moderate outer longitudinal tunica muscularis layers; and a true crop. In contrast, the esophagus of FT showed a thin epithelium, no muscularis mucosae, moderate inner longitudinal and thick outer circular tunica muscularis layers, and no true crop. In the proventriculus, the nature of the secretion in GGD was neutral, but that of FT was acidic and neutral. In the gizzard, the muscle coat of GGD by α-SMA had no muscularis mucosae, unlike FT, which had muscularis mucosae. In summary, there are many histologic differences between GGD and FT to meet their different physiologic needs, such as feeding.

Like many diurnal raptors, the American kestrel or sparrow hawk, Falco sparverius, possesses two foveae in each eye. In this study, we used fundus photography and reversed ophthalmoscopy to plot the projection of these foveae onto the visual field, together with other retinal landmarks such as the pecten and ora terminali. From such data, it was determined that the central monocular fovea (CMF) and temporal binocular fovea (TBF) were separated by 36 deg and that the kestrel has 58 deg of binocular overlap when the eyes are appropriately converged. Single-cell and multi-unit recordings were used to systematically explore the tectal surface and map receptive fields (RF) onto a hemispheric screen. A retinotopic map of the tectal surface was produced from such data and revealed an expanded representation for each fovea on the tectum and a systematic increase in RF size from fovea to periphery. The functional significance of this organization is discussed.

The numbers of sparrowhawks Accipiter nisus received for study at Monks Wood Research Station increased greatly between 1963 and 1992, then declined by 50% in 1992–97. The long-term increase reflected the national population recovery over this period and followed the reduction in the use of organochlorine pesticides. It was most marked in the eastern parts of Britain where the earlier population decline was greatest. The numbers of kestrels Falco tinnunculus received for study fluctuated greatly from year to year, and showed only a slight net increase over the study period. There was a marked increase in the late 1970s in eastern districts, the only areas where kestrels had obviously declined during the peak years of organochlorine use. The sparrowhawk carcasses revealed two peaks in recorded mortality: August–September, affecting mainly recently independent juveniles; March–April, affecting similar numbers of adults and juveniles. Kestrels showed no obvious seasonal peak in recorded mortality, but fewest carcasses were received in the early breeding season April–May. Among sparrowhawk carcasses, the sex ratio was significantly biased towards females (0.8 male to 1.0 female), but among kestrel carcasses the sex ratio was close to unity. Overall, 64% of sparrowhawks and 69% of kestrels were juvenile (= first year) birds, implying a mean first-year mortality in the two species of 64% and 69%. The proportion of juveniles among sparrowhawk carcasses increased during the study period (probably reflecting improved breeding success), but the proportion of juveniles among kestrel carcasses showed no long-term trend. The most important causes of recorded deaths in both species were collisions (65% for sparrowhawk and 35% for kestrel) and starvation (18% for sparrowhawk and 40% for kestrel). The frequencies of different mortality causes recorded among carcasses found were unlikely to reflect their frequencies in the population at large, but they did reveal changes over time. During 1962–97, deaths attributed to organochlorine poisoning and shooting declined in frequency, while accidental deaths increased in frequency, especially collisions with road vehicles in kestrels and with windows in sparrowhawks.