ALBERT

Description / Table of Contents: Zusammenfassung 1. Für Sylvia atricapilla und S. borin konnte gezeigt werden, daß das Aktivitätsmuster gekäfigter Vögel und die Fangverteilung freilebender Vögel sowie deren Körpergewichtskurven gut übereinstimmen. 2. Daraus ist zu folgern, daß die Verteilung der Fänge aus einer freilebenden Population das Aktivitätsmuster eines typischen Einzelvogels widerspiegelt. Ebenso stellt die gemittelte Körpergewichtskurve der Fänglinge den Tagesgang des Körpergewichts eines typischen Einzelvogels dar. 3. Nach unseren Ergebnissen kann für die untersuchten Größen und lokomotorische Aktivität und Körpergewicht von gekäftigen auf freilebende Vögel und umgekehrt geschlossen werden.

Description / Table of Contents: Summary It is known, that willow warblers of the northern racePhylloscopus trochilus acredula start fall migration at an earlier age than conspecifics of the southern racePh. t. trochilus. In this paper we have examined the question whether this difference is (1) caused by the different environmental conditions (e.g. photoperiod) to which northern and southern willow warblers are exposed within their respective breeding grounds, or (2) whether it is due to differences in the endogenous organization of the two races. Thirteenacredula from northern Sweden near the arctic circle and 17trochilus from southwest Germany were taken from the nest at an average of 9 days. Approximately one half of each group was subsequently kept in a constant 18:6 hour day, the other half in a constant 12:12 hour day. Plumage development, postjuvenile molt, and changes in body weight and migratory restlessness were investigated. The results are not in agreement with hypothesis (1): In their natural environment the early migrating northern willow warblers are exposed to longer photoperiods prior to fall migration than their southern conspecifics but in this experiment it was the shorter photoperiod that accelerated all processes investigated including migratory restlessness. On the other hand, the results are in agreement with hypothesis (2). Under either experimental condition,acredula began und terminated plumage development and postjuvenile molt at an earlier age thantrochilus. Moreover, in LD 18:6, the onset of Zugunruhe was considerably advanced inacredula as compared withtrochilus. Whether these differences are, in fact, genetically determined cannot be definitely decided until possible effects of early environmental influences are eliminated.

Description / Table of Contents: Summary 1. In the paper presented the following questions about omnivorous songbirds were investigated: 1) Are there seasonally changing preferences in animal and vegetable foodstuffs, independent of food supply, i. e., endogenously controlled? 2) If so, are such preferences related to special seasonal changes in the birds' physiology, especially to hyperphagia or fat deposition? 3) Are there differences in the preferences between typical and less typical migrants and non-migrating birds? 4) Which components of nutrition were preferred? 5) What is the physiological and ecological significance of such preferences? 6) What happens, if only animal or vegetable food is available? 2. The experiments were carried out from 1971–1975 with a total of 233 handraised and trapped experimental birds: 87 typical migrants(Sylvia borin), 98 less typical migrants(S. atricapilla), 38 partial migrants (30Erithacus rubecula, 8Turdus merula) and 10 non-migrating birds (Passer montanus) (sect. 2.1). 3. The types of food used were:Tenebrio-larvae, ant pupae,Noctuidae and a commercial insect-fodder as animal foodstuffs; and a series of different fruits and seeds as vegetable foodstuffs (sect. 2.2). Some of the feed was used fresh and some after deep freezing. The individual components of the diets in the experiments were weighed out or/and counted (sect. 2.3). The caloric values and ingredients of the different materials were determined and compiled from literature (sect. 3.4) and their suitability for the experiments was tested (sect. 4.4). 4. The questions raised were investigated in the long-term experiments with hand-raised birds, and in the short-term experiments with trapped birds. They were carried out under natural and constant light conditions. 5. Results 5.1. Proof of annual periodicities of food preferences (sect. 3.1) 1) Sylvia borin andS. atricapilla, under constant conditions and with a constant food supply showed regular spontaneous changes in the ingested amounts of animal and vegetable foodstuffs — for the first time in birds. These changes might be based on an endogenous periodicity. Perhaps, a circannual periodicity may be responsible. 5.2. Preferences for animal and vegetable food (sect. 3.1, 3.2) 1) Sylvia borin, Erithacus rubecula andTurdus merula did not prefer vegetable food to animal food in any experiment or at any season. 2) Sylvia atricapilla regularly favoured vegetables in a period which coincided with parts of the juvenile molt, the migratory restlessness of the first autumn migration and partly with the winter molt. The significance of this preference is not certain. In the most carefully investigated species,Sylvia borin, the highest intake of vegetables coincided with the winter molt. 3) Passer montanus regularly preferred seeds toTenebrio-larvae and showed few and no systematic changes in the ingested amounts of animal and vegetable foodstuffs during the seasons. 4) Hyperphagia during fat deposition and migratory periods was accompanied by an intensified intake of animal food whereas the intake of vegetables regularly decreased at that time. 5) Freshly trapped specimen ofSylvia borin, S. atricapilla andErithacus rubecula immediately developed preferences for unfamiliar animal foods (depending on the experimentTenebrio-larvae, ant pupae, commercial insect-fodder) and even unpopular animal food(Noctuidae) was to a certain extent preferred to well known fruits. 5.3. Preference of different vegetable food (sect. 3.2.2) 1) Sylvia borin preferred berries ofFrangula alnus andRubus idaeus. S. atricapilla favoured berries ofSambucus racemosa more, even when the birds had been hand-raised with fruits ofRubus idaeus. 2) Erithacus rubecula did not prefer any special fruit, not even the so-called „bread of the robin“ — the fruits ofEvonymus europaeus. 5.4. Exclusive feeding of animal food (sect. 3.3.1) 1) When fed exclusively with animal foodstuffs (and vitamins),Sylvia borin showed no alterations in behavior or the course of annual processes in a nine month experiment. 5.5. Exclusive feeding of vegetable food (sect. 3.3.2) 1) Feeding berries and other pulpy fruits toSylvia borin, S. atricapilla, Erithacus rubecula andTurdus merula resulted in a continuous and strong decline of the body weight from the first experimental day on. The body weight reached abnormally low values quickly, so that the birds became ill and died if no additional animal food was fed. 2) The rapidity of body weight decline was not altered when different fruits were fed. 3) Exclusive feeding of fruits was characterized at first by a low intake and relatively rapid weight loss and then later an increased intake and a slower weight loss. 4) The supply of drinking water (tested inSylvia atricapilla) did not effect the amount of fruits ingested. 5.6. Results on the physiological and ecological significance of animal and vegetable food (sect. 3.3.3, 4) 1) Subsequent feeding of animal foodstuffs resulted in an increase of the body weight which had been reduced by the exclusive feeding of fruits. 2) The observed weight loss in the case of exclusive feeding of fruits is probably caused by a lack of protein intake. 3) ForSylvia borin andErithacus rubecula fedad lib. on fruits, a supplement of only 3 gTenebrio-larvae/day was sufficient for maintenance of body weight. ForTurdus merula about 2–3 g was necessary (that is about 16, 19 and 3–4% respectively of the body weights). 4) The migratory species investigated, preferred principally animal foodstuffs during the periods of migration, when the intake of vegetable foodstuffs was simultaneously decreased. That held true for typical as well as for less typical migrants. These findings (and the observation that the investigated omnivorous songbirds were not able to maintain body weight, s. 5.5 above, much less to deposit fat when fed exclusively on berries and other pulpy fruits) refutes the hypothesis that songbirds shift to feeding on fruits in the migratory periods in order to render or to accelerate fat deposition. 5) It is concluded 1) that for the investigated omnivorous songbirds, feeding on berries and other pulpy fruits animal foodstuffs is a vital necessity and 2) that vegetable foodstuffs is a secondary or supplementary food for economic reasons: This supplementary food is necessary if animal food is scarce or in periods of high nutritive demands if animal food in sufficient quantities can only be obtained with excessive efforts. These conclusions are convincingly supported by observations and data from the wild and the laboratory which are dealt with in 1)–5) on pp. 181–186. 6) If the fruits are in ample supply, additional feeding on fruits enables omnivorous songbirds to winter in higher latitudes and thus to be at the breeding places in good time, and to get ready for migration in autumn and to rear successfully young of late broods even though the supply of animal food is only moderate. 5.7. General significance of the results and points (sect. 4) 1) With respect to the results obtained and to the now well known primary nature of animal food as foodstuffs for omnivorous songbirds, exterminations of insects should be further considered because they can lead to dangerous food shortage. 2) The lack of animal food, especially in winter, can lead to a dietary deficiency in omnivorous songbirds. Hence, reed should be preserved on principle because it is a major source of insect food for many omnivorous (and insectivorous) species. 3) In stopover places and winter quarters of omnivorous species, bushes with fruits which are suitable as supplementary food should be planted in a greater extent Suitable plants need first to be determined. 4) IvyHedera helix whose berries are a valuable supplementary food for omnivorous species should be protected and planted in certain areas. 5) In sect. 4.4 the carrying-through of the experiments, possible sources of errors and possibilities of the generalization of the results obtained are discussed in detail. 6) In sect. 4.6 open questions arising from the results obtained are compiled. Among other questions, it is important to determine whether the agricultural damages to plantations by omnivorous songbirds can be diminished by an unreduced or increased supply of animal food.

Description / Table of Contents: Summary 1. In the paper the choice of nest sites of the blackcap Sylvia atricapilla in spruce forests in SW-Germany is presented. This investigation is based on 834 nest record cards which have been collected by the amateur and professional coworkers of the Vogelwarte Radolfzell in the warbler program over the period 1968–1976. 2. In SW-Germany, the blackcap often nests in spruce forests: 22% of the nests were found in spruce forests or in groups of spruces. The blackcap nests in all types of spruce forests from very small trees to tall forests. 3. In the various types of spruce forests the mean nest heights show only relatively little variation compared with that of the different nest bearing substrata: in small trees the nests are placed in green branches, in higher trees to a great extent also in the thickets of dried up branches, in tall forests either in the underwood or in spruce branches hanging down near to the ground. 4. Obviously, in the blackcap the spruce is a preferred nest site for relatively early broods. Whether, for instance, covering or special microclimatic conditions might be reasons for this is open. 5. In tall mixed forests without underwood it is often the nesting in spruce trees which enables the blackcap to settle in woods such as these. 6. The blackcap is a good example for adaptive choices of nest sites in varying conditions of one type of vegetation as the spruce forest. 7. Finally, regional differences of blackcaps' nesting in spruces are shown.

Description / Table of Contents: Summary In long-term experiments resident species and less typical migrants were investigated for endogenous factors involved in their annual periodicity; in detail:Parus cristatus (10 birds in LD 10 : 14, 2 years),Passer montanus (15 birds in LD 10 : 14, 4 years; 20 birds in LD 12 : 12, 2 years, and 20 birds in LD 14 : 10, 2 years),Loxia curvirostra (10 birds in LD 12 : 12, 4 years), andSylvia conspicillata (4 birds in LD 10 : 14, 2 years). Most of the experimental birds were hand-raised. All four species showed endogenous annual (circannual) rhythms with period lengths of regularly less than 12 months as in earlier studies. The extent of the observed circannual rhythms varied considerably among the different species and the various annual processes investigated: InParus cristatus, Loxia curvirostra andSylvia conspicillata all experimental birds showed circannual moult rhythms. InPasser montanus, in LD 12 : 12 no endogenous moult rhythm could be observed, in LD 10 : 14 only to a small extent and also in LD 14 : 10 only in about 30 % of the experimental birds. In addition to moult circannual periodicity could only be found in the testis cycle ofPasser montanus (2 out of 5 birds in LD 10 : 14) and in the course of body weight inLoxia curvirostra (at least 3 out of 10 birds). In addition to the reported proofs of circannual rhythms it is probable that endogenous annual rhythmic events are also involved in the control of the testis cycle ofLoxia curvirostra and in the ovarial cycle ofPasser montanus. As in earlier experiments moult has proved to be the annual event that is most obvious controlled by circannual rhythms. It is open as to whether moult is controlled by especially marked endogenous rhythms or whether the moult rhythms merely are best expressed in the chosen experimental conditions. The species investigated showed marked differences in the amount of observed circannual rhythms. Furthermore, they showed less circannual rhythms than typical migrants studied in earlier investigations. These differences might have different causes: in resident birds and less typical migrants circannual rhythms could only appear in very specific experimental conditions (for details, s. discussion), or these rhythms could in these birds in general be less developed than in typical migrants. Presently it is impossible to decide between these two possibilities, but a generally less developed circannual rhythmicity in resident birds and less typical migrants seems to be more likely.