Abstract. We evaluated cuttlefish (Sepia officinalis) responses to three teleost predators: bluefish (Pomatomus saltatrix), summer flounder (Paralichthys dentatus), and black seabass (Centropristis striata). We hypothesized that the distinct body shapes, swimming behaviors, and predation tactics exhibited by the three fishes would elicit markedly different antipredator responses by cuttlefish. Over the course of 25 predator-prey behavioral trials, 3 primary and 15 secondary defense behaviors of cuttlefish were shown to predators. In contrast, secondary defenses were not shown during control trials in which predators were absent. With seabass-a benthic, sit-and-pursue predator-cuttlefish used flight and spent more time swimming in the water column than with other predators. With bluefish-an active, pelagic searching predator-cuttlefish remained closely associated with the substrate and relied more on cryptic behaviors. Startle (deimatic) displays were the most frequent secondary defense shown to seabass and bluefish, particularly the Dark eye ring and Deimatic spot displays. We were unable to evaluate secondary defenses by cuttlefish to flounder-a lie-and-wait predator-because flounder did not pursue cuttlefish or make attacks. Nonetheless, cuttlefish used primary defense during flounder trials, alternating between cryptic still and moving behaviors. Overall, our results suggest that cuttlefish may vary their behavior in the presence of different teleost predators: cryptic behaviors may be more important in the presence of active searching predators (e.g., bluefish), while conspicuous movements such as swimming in the water column and startle displays may be more prevalent with relatively sedentary, bottomassociated predators (e.g., seabass).

Summary A visit was made to Malamfatori, on the western shore of Lake Chad, Nigeria, from 22 March to 13 April 1967, with the principal aim of studying Palaearctic migrants in relation to the environment. About 2,400 Palaearctic migrants of 29 species were mist‐netted in beds of bulrush Typha australis and thickets of saltbush Salvadora persica. Some 300 of these were collected for fat analysis; the remainder were released after measurement and ringing, and provided 275 retraps during the course of the study. Data were supplemented by further netting by A. J. Hopson in late April and May. Yellow Wagtails Motacilla flava, Sedge Warblers Acrocephalus schoenobaenus and Whitethroats Sylvia communis were abundant and were studied in greater detail than other species. Yellow Wagtails fed almost exclusively on midges, particularly the abundant Tanytarsus spadiceonotatus. Sedge Warblers fed on small insects and spiders, and Whitethroats on Salvadora fruits. Sedge Warblers and some other chiefly insectivorous species turned to a diet including berries shortly before emigrating. Changes in weight during the course of the day were difficult to investigate, but were probably bimodal. Good correlations of weights with wing‐lengths were obtained for species for which many data were available. Pre‐migratory fattening did not occur synchronously in all populations of a species, but once it started in an individual it proceeded at a constant rate of 0.2 g/day in Sedge Warblers and 0.6 g/day in Whitethroats. Predation pressure probably ensured that individuals emigrated immediately they attained their maximum pre‐migratory weight, although some Sedge Warblers and Whitethroats left the area before attaining maximum weight. Differences between the mean weight curves of first‐caught and retrapped birds are discussed, and it is concluded that in some species there were both through‐migrant and temporarily‐resident populations at Malamfatori. The mean weights per day of Whitethroats, Sedge Warblers and also Reed Warblers A. scirpaceus were falling in late March, and slight changes in the weather, particularly temperature, may have been responsible. In mid‐April there was a “rush” of lean Whitethroats, which are thought to have originated to the SW in Nigeria. Yellow Wagtails, Sedge Warblers and Whitethroats deposited up to 40% fat/live weight; Sand Martins Riparia riparia had up to 28%, and a small sample of Ruffs Philomachus pugnax up to 17%. In the case of Sedge Warblers, fat reserves were sufficient for crossing the Sahara both to the north and to the northeast. Contrary to the findings in some previous lipid studies, the fat‐free dry weight and water content increased during fattening. The fat‐free dry weight increase was about 34% in Yellow Wagtails, 18% in Sedge Warblers, and 35% in Whitethroats. The tissues involved in this increase were not investigated, but a study of Yellow Wagtails at Malamfatori in 1968 (in prep.) suggests that the pectoral muscles hypertrophy during fat deposition sufficiently to account for nearly all of ...

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Summary Owing to the regular alternation of wet and dry seasons and to the relatively simple arrangement of vegetation zones, migration is a well‐developed phenomenon in the northern tropics of Africa. Nigeria is well placed for its study. While a vast amount remains to be learned, a systematic treatment of the 672 Nigerian bird species shows that at least 126 of them are migrant. Species newly shown to be migratory include the sunbird Nectarinia pulchella, the bunting Fringillaria (Emberiza) tahapisi, and the sparrow Gymnoris (Petronia) dentata, and corroborative evidence is adduced for many more. New interpretations are placed on the movements of the bustard Neotis denhami, the Painted Snipe Rostratula benghalensis, and other species. Most families that are migrant in the temperate zone (e.g. storks, cuckoos, nightjars, hirundines) have several migrants among their tropical representatives, except flycatchers, thrushes, warblers and shrikes. Important tropical migrant families include the kingfishers and sunbirds. The following ecological correlates emerge: migration appears to be more important at lower than higher trophic levels in the ecosystem; only one primary lowland rain forest and one montane forest species migrate; 95% of African migrants in Nigeria inhabit the five savanna zones, where the 120 migrants comprise 28% of the avifauna; most savanna migrants cross one, two or three vegetation zone boundaries; few are restricted within a single zone or cross four boundaries; twice as many savanna species are eurytopic (habitat‐tolerant) as stenotopic (habitat‐tied), and twice the proportion of eurytopic as stenotopic species are migrant; the majority of migrants move so as to avoid the winter drought in northern Nigeria (insectivores being little affected) and also the heaviest summer rains in southern savannas; migration is initiated by climatic factors such as rains, dry desert winds, etc. Three to six Nigerian species cross the Equator, but the stork Anastomus lamelligerus is shown to breed in Nigeria and the Chad basin and may not be a trans‐equatorial migrant. A quail, a crake, a coucal and five cuckoos have space‐time distribution patterns (motograms) in Nigeria that suggest equatorial migration. Motograms figured for 60 species show great variation. Nearly all land‐bird migrants move with the progression of the sun and the inter‐tropical front, north in spring and south in autumn. The basic pattern is thus a summer wet‐season range at higher latitude than the winter dry‐season range, and specific patterns vary according to the absolute and relative latitudinal limits af each season, and to speed and dates of migration. Comparison of congeneric migrants having different breeding seasons or motogram patterns suggests that a specific migration pattern is fixed by ecological necessity, and reproduction occurs at that time in the year when the species is stationary longest. Breeding seasons may span migration periods, leading to two‐stage early‐rains migration in e.g. the kingfisher Halcyon leucocephala. ...