Solar cues in the migratory orientation of the Savannah sparrow, Passerculus sandwichensis

Results clearly implicate the setting sun as a critical source of directional information in the migratory orientation of the savannah sparrow, Passerculus sandwichensis. Savannah sparrows allowed a view of both sunset and stars displayed oriented behaviour in biologically meaningful directions during spring and fall seasons. When the same individuals were denied a view of sunset, and tested under the stars alone, disorientation characterized their behaviour. Furthermore, birds allowed a view of sunset, but tested under ‘overcast’ night skies (no stars visible), displayed well-oriented behaviour indicating the sufficiency of sunset. Experiments in which the migrant's internal chronometer was shifted suggested a fixed-angle (menotactic) response to the sunset cue rather than a time-compensating compass mechanism. I believe stars are valuable to this migrant as celestial reference points. Orientational information gained at the time of sunset is transferred to stars on a nightly basis. The relationship between solar and stellar cues is apparently hierarchical in the savannah sparrow. Information necessary to select the appropriate migratory direction is gained from the primary cue, the setting sun, while maintenance of that heading is dependent on a secondary cue, probably the stars.     

Hippocampal lesions do not impair the geomagnetic orientation of migratory savannah sparrows

The avian hippocampal formation is known to participate in naturally occurring spatial behavior such as homing in pigeons and cache recovery in food storing passerines, but its participation in the often spectacular migrations of birds remains uncertain. As a first investigation into the possible role of hippocampal formation in migration, the effect of hippocampal formation lesions on the geomagnetic migratory orientation of Savannah sparrows was examined. When tested indoors, hippocampal formation-lesioned sparrows were able to orient in an appropriate migratory direction indicating no necessary role for hippocampal formation in geomagnetic migratory orientation. However, hippocampal formation-lesioned birds displayed significantly less migratory (nocturnal) activity, a result that inspires further study. Accepted: 25 August 1999     

Intraspecific acoustical interference in the white-throated sparrow (Zonotrichia albicollis)

Intraspecific acoustical interference was studied in the white-throated sparrow (Zonolrichia albicollis). It was found that individuals avoid singing during a song of a conspecific. The effect is significantly greater with neighbours that are closer to them. The evolutionary implications of this phenomenon for the properties of song in Z. albicollis are discussed.     

Finite state grammars for dialects of the advertising song of the savannah sparrow (PasserculusSandwichensis)

Right-linear finite state grammars were extracted for song sequences of Savannah Sparrows (Passerculus sandwichensis) from Ontario and Nova Scotia. The Nova Scotia grammar was found to be longer than the Ontario grammar (possess more rewrite statements) and allow for the production of sequences containing consecutive trills. These differences are discussed with respect to genetic and environmental factors shaping song behaviour in the two regions. Limitations of a nonstochastic finite state grammar procedure are also addressed.     

Field studies of avian nocturnal migratory orientation II. Experimental manipulation of orientation in white-throated sparrows (Zonotrichia albicollis) released aloft

Migrant white-throated sparrows (Zonotrichia albicollis) were released from boxes carried aloft by balloon and tracked with radar. All birds were released on clear nights when winds were light and opposed to the normal migration direction for the season. Birds were treated in one of two ways: Lens birds were fitted with frosted lenses prior to release; No Lens birds were released without lenses. No Lens birds that engaged in straight and level flight generally headed in the predicted migratory direction and as a group were not oriented with respect to wind direction. Lens birds did not head in the predicted migratory direction, but instead oriented downwind. This orientation behaviour is consistent with the relationship of orientation cues inferred from the field observations described in part I of this paper. The data show that flying birds deprived of all detailed form vision can determine wind direction.     

Species-universal microstructure in the learned song of the swamp sparrow (Melospiza georgiana)

A swamp sparrow song is a 2-s string of about 10 identical syllables, each made up of two to five distinct notes. Naturally-occurring syllables are highly polymorphic. The development of syllable patterning is strongly influenced by imitation. Analysis of 452 songs indicates that, whether simple or complex, all syllables were assembled from the same species-universal set of note types, consisting of six basic categories. Two populations studied intensively, 1000 km apart, differed in the number of notes per syllable and the ordering of note types within a syllable. It appears that song dialects can be defined in the swamp sparrow by reference to these features. The process of song learning in the swamp sparrow thus consists of the selection of a particular number, timing and sequence of notes from a limited set of types. While some degree of selection of within-type note variants is possible, the structure of the major categories of swamp sparrow note types is in large degree genetically preordained.     

Autumn migratory orientation and displacement responses of two willow warbler subspecies (Phylloscopus trochilus trochilus and P. t. acredula) in South Sweden

Topography and historical range expansion has formed a so-called migratory divide between two subspecies of willow warbler (Phylloscopus trochilus) in central Scandinavia. The autumn migratory directions of individuals assigned molecularly to both subspecies and possible hybrids were recorded using orientation cage experiments in southwest and southeast Sweden. We found pronounced differences in willow warblers’ orientation in respect to genotype. The mean directions registered in the control experiments were in accordance with the ringing recoveries and analyses of stable isotopes for Scandinavian willow warblers. With the same individuals we performed displacement experiments between both sites. They resulted in non-significant orientation, which could be explained by the intermediate distance of the displacement or reactions to housing, transportation and location. On a separate set of birds we tested whether stress following transportation could explain the disorientation and found that orientation before and after transport was unchanged. Experimental studies of effects of intermediate displacements across longitudes and studies of orientation of hybrid individuals in the zones of migratory divides are crucial for understanding the mechanisms underlying orientation behaviour. Our work further stresses the importance of knowing the migration genotype of a particular bird under study, in order to correctly evaluate expected migration routes.     

Seasonal differences in behavior patterns of the migratory white-throated sparrow

Avian migration and associated changes in behavior patterns occur on a seasonal basis and are regulated by both circadian and circannual clocks. It is well known that seasonally migrating birds must alter the temporal partitioning of behaviors in order to successfully complete nocturnal migration, although the precise changes in allocation have not previously been examined. Because of the difficulties related to the study of bird migration in the wild, many studies regarding the physiology of migration have been performed in captivity, where nocturnal migratory restlessness is readily observable at the appropriate times of the year. Even so, quantifying the amount and timing of daily behavioral rhythms in migrating and non-migrating individuals has not previously been performed. We used video recordings of a common nocturnal migrant, the white-throated sparrow (Zonotrichia albicollis), to generate a basic ethogram and to chart the timing and frequency of occurrence of each behavior in order to compare migrant individuals with non-migrating birds. Our study suggests that the specific allocation of behaviors are altered during migration and that these changes might contribute to the development of the “migratory syndrome”.     

Feeding impairs chill coma recovery in the migratory locust (Locusta migratoria)

Low temperature causes loss of neuromuscular function in a wide range of insects, such that the animals enter a state known as chill coma. The ability to recover from chill coma (chill coma recovery time) is often a popular phenotype to characterise chill tolerance in insects. Chill coma in insects has been shown to be associated with a decrease in haemolymph volume and a marked increase in [K⁺], causing dissipation of K⁺ equilibrium potential and resting membrane potential. High potassium diet (wheat) has also previously been shown to increase haemolymph [K⁺] in Locusta migratoria leading to sluggish behaviour. The present study combined these two independent stressors of ion and water homeostasis, in order to investigate the role of K⁺- and water-balance during recovery from chill coma, in the chill sensitive insect L. migratoria. We confirmed that cold shock elicits a fast increase in haemolymph [K⁺] which is likely caused by a water shift from the haemolymph to the muscles and other tissues. Recovery of haemolymph [K⁺] is however not only reliant on recovery of haemolymph volume, as the recovery of water and K⁺ is decoupled. Chill coma recovery time, after 2 h at −4 °C, differed significantly between fasted animals and those fed on high K⁺ diet. This difference was not associated with an increased disturbance of haemolymph [K⁺] in the fed animals, instead it was associated with a slowed recovery of muscle [K⁺], muslce water, haemolymph [Na⁺] and K⁺equilibrium potential in the fed animals.     

Circadian and masking control of migratory restlessness in Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii)

Avian migration is a seasonal activity that requires intricate timing on both an annual and daily basis. With increasing evidence for endogenous regulation of daily activities in migrant species, we tested whether a circadian oscillator may be involved with the expressions of daily locomotor activities and specific behaviors of the long-distance migrant, Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii). Our previous studies have identified both daytime and nighttime behavioral patterns under a photoperiod of 18L:6D. In 2 separate trials, birds in the vernal migratory life-history stage were exposed to constant dim light, (DD)dim, and constant bright light, LL, while locomotor activity and behavioral observations were collected. Under (DD)dim, the daytime behaviors that included active and quiescent components observed under 18L:6D were lost as migratory restlessness, the intense nighttime activity, persisted nonstop for 36.4 h. Furthermore, the specific behaviors of migratory restlessness that are normally confined to the dark phase of 18L:6D, beak-up and beak-up flight, were expressed also during the subjective day of (DD)dim. Birds exposed to LL retained similar patterns of activity to the 18L:6D condition for 3 days, after which they became arrhythmic. Behavioral observations of intense locomotor activity observed during the subjective night of LL revealed no beak-up and beak-up flight. Thus, the complete expression of migratory restlessness that includes beak-up and beak-up flight may not be regulated by a circadian oscillator but instigated by very low light intensity. Locomotor activity and associated daytime behaviors appear to be influenced by a circadian oscillator, given their persistent patterns under LL. Therefore, we suggest that the separate components of migratory behavior are regulated differentially by a circadian oscillator and ambient lighting conditions.     

Song switching and agonistic stimulation in the song sparrow (Melospiza melodia): five tests

Male song sparrows in southeastern Ontario have repertoires of five to 11 distinct song types. The singer repeats each song type a variable number of times before switching to another type. Analysis of territorial singing suggested that rate of switching song types is positively correlated with intensity of agonistic stimulation, where ‘agonistic’ signifies conflict-related. The song-switching hypothesis was tested with playback experiments which varied stimulus intensity in five different ways: (1) presence or absence of song stimuli; (2) addition of visual to auditory stimuli; (3) location of the song stimulus 20 m inside or outside territory; (4) nesting phases of the subjects; and (5) switching rate and rate of novel song type production of the playback (i.e. stimulus versatility). The subjects' switching rates and flight rates consistently increased with greater stimulation, although song rate tended to remain unaffected. The signalling of response intensity through adjustments in switching rate exemplifies how song repertoires function in agonistic communication.     

Sunset and the orientation of European robins (Erithacus rubecula)

The migratory orientation of European robins (Erithacus rubecula) in autumn was tested immediately after sunset and also after the beginning of astronomical darkness. In twilight tests under clear skies, the birds selected an appropriate migratory direction. During the course of autumn, along with the shift of sunset azimuth, the orientation of birds also shifted, always in a counter-clockwise direction. Although this shift of orientation was not statistically significant, the difference between the mean direction and the sunset was the same for each autumn period. This suggests that the migratory direction was selected on the basis of menotactic orientation re the setting sun. Random directions were observed under solid overcast skies as well as during tests under starry skies, begun after all trace of the sunset position had disappeared.     

Fate and effects of the trehalase inhibitor trehazolin in the migratory locust (Locusta migratoria)

Trehalose is the main haemolymph sugar in many insect species. To be utilized trehalose must be hydrolysed into its glucose units by trehalase (EC 3.2.1.28). Inhibitors of trehalase have attracted interest as possible pesticides and tools for studying the regulation of trehalose metabolism in insects. To make full use of these inhibitors requires knowledge of their fate and effects in vivo. To this end we have measured trehazolin in locusts using a method based on the specific inhibition of a trehalase preparation. After injection of 20 μg, trehazolin decreased in haemolymph with a half-life of 2.6 days and after 10 days almost 95% had disappeared. Trehazolin did not reach the intracellular water space of locust tissues, but appeared with full inhibitory potency in locust faeces, suggesting that it was not metabolized, but quantitatively eliminated via the gut. Haemolymph trehalose increased transiently upon trehazolin injection, it was maximal after 3 days, then decreased and reached control level after 10 days. Inhibition of flight muscle trehalase by trehazolin was prolonged and still conspicuous 21 days post injection, suggesting that trehazolin inhibits trehalase activity irreversibly in vivo and that recovery requires de novo enzyme synthesis.     

Flock feeding and time budgets in the house sparrow (Passer domesticus L.)

A winter population of house sparrows at a farm fed on barley seed in two distinct types of habitat: cattlesheds and open fields. The risk of predation was apparently higher in the fields where birds scanned more frequently than in the cattlesheds and where scanning was negatively influenced by flock size but positively influenced by distance from cover. Individual time budgets were more influenced by flock size than by seed density in the fields but more influenced by seed density than by flock size in the cattlesheds. Higher rates of scanning resulted in greater flock vigilance and longer flight distances in the fields but flight distance was negatively influenced by the density of seeds on which birds were feeding.     

The role of egg pod foam and rearing conditions of the phase state of the Asian migratory locust Locusta migratoria migratoria (Orthoptera, Acrididae)

Coloration phase state, morphometrical ratios and the numbers of mature oocytes of Locusta migratoria migratoria were examined in a series of experiments to determine the means by which phase characteristics are passed to the next generation. Washing with distilled water of eggs from egg pods laid by gregarious crowd-reared females resulted in solitarization of the hatchlings after their isolation, indicating that a factor present in eggs encapsulated in foam is causal to gregarization. Such locusts showed a significant shift towards the typical solitarious body coloration, morphometry and number of mature oocytes as compared to locusts resulting from unwashed eggs. Gregarious coloration, morphometrical ratios and oocyte numbers could be partially restored when hatchlings from washed eggs were regrouped. When gregarious locusts were reared in isolation, they showed a solitary body color, whereas, morphometry and oocyte numbers were not affected by isolation.     

Sexual behaviour and novel stimuli in male japanese quail (coturnix coturnix japonica)

Sexual performance levels following the presentation of a novel stimulus were examined in male Japanese quail. During a 1-hr observation period males were presented either with a new stimulus female each 20 min, with the same female removed briefly at 20-min intervals or with the same female left undisturbed. Although the latency to grab the neck of the famel was shorter in the group receiving a fresh female after 20 min, the overall number of completed copulations was unaffected by the treatments. It is concluded, therefore, that novelty is not an important factor governing sexual performance levels of male Japanese quail under these test conditions.     

Biochemical stimuli for feeding in Acanthaster planci (L.)

The typical feeding response of the Crown of Thorns Starfish Acanthaster planci (L.) can be induced by mucoproteins of molecular weight greater than 200,000 daltons found in mucus obtained from corals of the genera Acropora and Fungia.     

Generalization and discrimination of positive and negative acoustic stimuli in the common carp (Cyprinus carpio)

Groups of common carp (Cyprinus carpio) were trained for 33 days to discriminate between two acoustic signals differing in frequency and temporal pattern. One signal (positive stimulus) was reinforced by food, while the other (negative stimulus) was not rewarded. When exposed to 3 positive and 3 negative stimuli per day (training Paradigm 1) the fish responded similarly to the two signals. When daily negative stimuli outnumbered positive stimuli (3 positive and 33 negative, training Paradigm 2) the fish responded similarly to the two signals for the first 2 weeks and then began to discriminate between them. Discriminatory response was statistically significant from Day 21 of training. After 33 days, training was switched from Paradigm 2 to Paradigm 1 and the fish maintained their discriminatory capability. The results are interpreted in terms of anticipatory frustration and risk management.