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Numerous field studies indicate that food supplementation of birds can advance laying date. In addition, laboratory studies, though less common, suggest that altering the amount of food, the predictability of food, or food type can affect reproductive physiology. American Goldfinches ( Spinus tristis , formerly Carduelis tristis (L., 1758)) breed in late summer when thistle (Cynareae) seeds become abundant, suggesting that specific food types may affect their reproductive physiology. We tested whether supplementation with preferred seeds would affect reproductive physiology of male and female American Goldfinches. Birds were photostimulated and fed a standard pellet diet, or supplemented with a variety of preferred seeds. Supplemented females developed larger ovarian follicles. Supplemented males had higher levels of plasma testosterone, but only if they were also housed with a female. These results suggest that preferred seed types can act as a supplementary cue in this species, and fine-tune photoperiod-driven changes in reproductive physiology.

Digestive efficiency (DE) is influenced by many factors including food type or quality. Assimilation efficiency (AE) and DE of 12 captive harp seals (Phoca groenlandica) were estimated for five prey types in large outdoor seawater tanks. In trials of > 9 days' duration, the seals were fed Atlantic cod (Gadus morhua), Arctic cod (Boreogadus saida), Greenland halibut (Reinhardtius hippoglossoides), Atlantic herring (Clupea harengus), and capelin (Mallotus villosus). Fish were marked with inert tracers so that faecal samples could be matched to individual animals. AE (digestibility of dry matter) was estimated from the relative concentration of Mn2+in food and faeces. DE (digestible energy) was estimated from the relative concentrations of both Mn2+and energy in food and faeces. AE and DE values were high, but varied among the fish species (DE: Atlantic cod 93.5%; Arctic cod 93.5%; halibut 94.7%; capelin 95.7%; herring 96.6%). Both estimates of digestive efficiency were positively correlated with prey energy density. For most prey, AE and DE were not correlated with meal size, number of prey in a meal, size of prey, or seal body mass. However, digestive efficiency was greater in seals fed smaller Atlantic cod, or meals of greater mass. Quantifying estimates of digestive efficiency is important for formulating energy-based population consumption models, and so should be improved. It is recommended that more pinniped species be studied in captivity, that experiments last longer, and that the number of individuals studied be increased so that individual differences can be investigated.

Standardized indices (I) have been created to determine and analyze individual food preferences in choice tests between A types of food presented in the form of N items entirely consumable within the course of one test. For each food type, I represents the ratio between the cumulative area under the curve of the proportion of items consumed as a function of the order in which are consumed the A∙N items, and the sum of the areas for all A items. I varies from 0 (for food in which no item is consumed) to 1 (for food items consumed exclusively); I = 1A for A types of food for which there is no preference; the sum of all indices (I) for all A foods equals 1 in all tests. These standardized indices have been used in tests on Barbary doves (Streptopelia risoria) to study intra-individual coherence and interindividual correspondance in reference to preferences for canary grass (Phalaris canariensis L.), oats (Avena sativa L.), wheat (Triticum vulgare Vill.), hemp (Cannabis sativa L.), and millet (Panicum miliaceum L.).[Translated by the Journal]

A laboratory experiment and natural-diet study were conducted to examine the feeding ecology and importance of food type for growth of Gammarus fasciatus from the Ohio River. To determine effects on growth, amphipods were fed four diets: (1) filamentous algae (Cladophora) and diatoms, (2) dead animal matter (chironomids), (3) coarse particulate organic matter (CPOM), and (4) fine particulate organic matter (FPOM). Organic matter was obtained by shredding preconditioned sycamore leaves (Platanus occidentalis). Growth was evaluated from weekly measurements of head length. There were no significant differences in growth among food types before week 3 of the experiment, but from week 4 to week 6, amphipods fed algae and dead animal matter were significantly larger than those maintained on CPOM and FPOM. Gut analysis of natural populations showed that G. fasciatus consumed all food types used in the laboratory study. The weighted proportions of filamentous algae and animal matter in riverine populations increased consistently from smallest to largest size-class. The availability of, and ability to use, algae and animal matter by G. fasciatus benefits natural populations in large rivers by enabling them to exploit seasonal changes in the relative abundance of different food sources.

The food habits of animals may be studied in the laboratory or in the field. Field studies describe diet selection of populations but do not permit analysis of the factors causing individual variation in the foraging behaviour of animals. Although numerous indices have been developed to compare use and availability of foods in field diets of animals, little attention has been given to laboratory approaches for comparing food choices. Tests of food choice must account for the order, consumption rate, and total amount of each food type eaten. Current measures fail to account for one or more of these parameters. This often results in highly ambiguous preference rankings, making comparisons among individuals or species difficult. To solve this problem, I propose using the area under the curve of the cumulative proportion eaten versus time for each food type. This index may be used to assess individual variation and determine the relative importance of each major component of the diet selection process in animals.

The forage ratio and Ivlev's electivity index as measures of preference by predators of different prey or food types were shown by Jacobs to depend on their abundance. Modifications proposed by Jacobs are shown here to be similarly affected by the abundance. However, an index of the preference that is indeed independent of the prey abundance can be based on standardized forage ratios, standardized so that the forage ratios for the different prey species sum to one. Key words: index of preference, prey selection, food selection, predator–prey relationship

The feeding ecology of ring-billed gull chicks from hatching to fledging was studied on an insular colony near Presqu'ile Provincial Park, Ontario, during the summer of 1977. A principal objective was to determine changes in food type and frequency of feedings during chick development and among temporally spaced broods.Two daily peaks in chick feeding occurred with the first shortly after sunrise and the second just prior to sunset. The frequency at which chicks were fed peaked when they were 4 days old and declined steadily thereafter. Chicks younger than 5 days were fed insects and fish while chicks older than 5 days were fed mainly fish. Seasonal variation in food type fed to chicks changed from insects and fish early in the season to predominantly fish late in the season. The incidence of earthworms in feedings correlated with preceding periods of high humidity or rain.

Food study based on the stomach analyses of 551 chinook salmon (Oncorhynchus tshawytscha) and 659 coho salmon (O. kisutch) collected from the various localities along the southern British Columbia coast during the summer of 1957 revealed that herring followed by crustaceans formed the most important items of the diet of the two species. Coho salmon exhibited a more pelagic and varied diet than chinook salmon caught in the same area. Definite seasonal fluctuations in the composition of food and feeding intensity were noticed. Considerable amounts of Crustacea were taken in early summer months and after that fish assumed importance.Qualitative and quantitative differences in the feeding of these two species on the east and west coasts of Vancouver Island appear to warrant the establishment of two food type areas, Although herring constitute the major food item of both spring and coho salmon, evidences are presented in support of the hypothesis that a change in herring stock is not likely to affect salmon abundance in British Columbia coastal waters.

Fecal pellets produced by larvae of Enallagma ebrium and Ischnura verticalis given ad libitum feedings of enchytraeid worms were heavier than pellets produced by larvae given ad libitum feedings of Daphnia magna. Dependence of pellet weight on food type has marked implications for indices of food limitation for larval dragonflies.