Elevated Perches Research Articles

Roosting behaviour of the endangered Sichuan Hill-partridge Arborophila rufipectus during the breeding season

AbstractRoosting behaviour in diurnal ground-dwelling birds is important to their conservation as they are particularly vulnerable to predation when on their roosts. In 2005, we studied the roosting behaviour of the globally ‘Endangered’ Sichuan Hill-partridge (Arborophila rufipectus) in Laojunshan Nature Reserve, southwest China, a site dominated by evergreen broadleaf forest. Our study showed that the birds roosted on elevated perches and roosting behaviour was associated with social organization. Breeding males roosted alone within their territories before mating or during the female's involvement in incubation, but at other times they roosted with the female bird. After hatching of the brood, the adult males roosted on the ground close to the brooding female for about two weeks. After this time the male left the female and chicks to roost elsewhere in the territory. High vegetation cover around the perch site was a key predictor of roosting sites for the partridges. Only six out of 84 tree and shrub species were typically used by the roosting birds, although individual roosting plants varied from night to night. The median height of roosting plants was 6.9 (3.8–10.5) m, which was significantly lower than many shrubs within the breeding territory. Perches were 1.7–6.4 (median = 2.7) m from the ground and independent of roost tree height, suggesting an optimum roosting height. The partridges preferred roosting sites with denser shrub vegetation. In terms of the species' conservation, our results highlight the importance of protecting primary forest that contains suitable roosting trees and shrubs.

Effectiveness of Avian Predator Perch Deterrents on Electric Transmission Lines

ABSTRACT A new high‐voltage transmission line in north‐central Nevada, USA, was considered a potential threat to greater sage‐grouse (Centrocercus urophasianus) because avian predators are attracted to and hunt from elevated perches. As a mitigation measure, perch deterrents were installed on the transmission line towers at the time of construction; in addition, 2 existing high‐voltage transmission lines were retrofitted with deterrents. Previous published studies have investigated the efficacy of perch deterrents in preventing or reducing electrocution of avian predators and fecal contamination of insulators, but none have evaluated deterrents as a means of eradicating perching on towers. We conducted point transect surveys and perching‐duration observations of corvids and raptors and determined that although perch deterrents did not prevent perching, the perching duration of raptors on the deterrents was reduced compared to other perching substrates. Perching of raptors indicated that some hunting most likely took place from the towers; therefore, the deterrents did not completely obviate the threat that avian predators posed to greater sage‐grouse. Although the deterrents reduced the probability of avian predators perching on the towers, avian predators overcame the deterrents to take advantage of the height of the towers where no other perches of similar height existed. The perch deterrents as designed did not have the desired short‐term effect on avian predators, but further monitoring may reveal longer‐term effects and distinguish perching behaviors specific to different species of avian predators.

A new morphologically cryptic species of forest frog (genus Platymantis) from New Britain Island, Bismarck Archipelago

We describe a new species of forest frog in the genus Platymantis from New Britain Island, Bismark Archipelago, Papua New Guinea. The new species is a morphologically cryptic form that has masqueraded for almost four decades under the name P. schmidti (formerly P. papuensis schmidti, Brown & Tyler, 1968). The new species is microsympatric with the geographically widespread P. schmidti at two known localities. We diagnose the new species on the basis of its distinctive advertisement call and slight but consistent differences in body size and proportions. Calling males of the new species appear to prefer more elevated perches than do males of P. schmidti and the new species may exhibit a greater extent of sexual size dimorphism.

Context Dependent Territory Defense: The Importance of Habitat Structure in Anolis sagrei

AbstractTerritoriality is a potentially costly endeavor, and several mechanisms for mitigating the costs of territoriality have been investigated in the wild. For example, territory owners can reduce the costs of defending territory boundaries by prioritizing defense of the most valuable areas within territories, investing less energy in low quality areas. We staged pairwise encounters between adult male lizards on natural territories in the wild, to test whether male brown anoles, Anolis sagrei, would differentially defend certain regions of their territories over others. Based on our observations that male A. sagrei spend most of their time on elevated perches on tree trunks or branches compared with sites on the ground, we predicted that territory residents would respond more aggressively to territory invasions that took place on elevated perches than to invasions on the ground. We measured significant differences in the behavior of residents following invasion on the ground vs. on the elevated perches, and results partially supported our hypothesis. Males performed more displays and approached intruders more often when territory invasion took place on the ground, but were quicker to attack intruders that entered territories on elevated perches. Our hypothesis was only partially supported, potentially indicating that elevated perches are preferred as outposts to monitor valuable sites on the ground. Our study provides evidence that territory defense varies not just among individuals, but also within individuals at different locations in a territory.

Ecomorphological variation in foraging behaviour by Puerto Rican Anolis lizardsAnolislizard ecomorphs

Ecomorphs of Anolis lizards evolved convergently via niche partitioning in separate radiations. Each ecomorph has a suite of traits including body size, morphology, microhabitat, anti-predatory behaviour, and foraging, but foraging movements of ecomorphs have not been characterized quantitatively. Data are presented on aspects of foraging for seven species representing four ecomorphs in the cristatellus series from Puerto Rico. Using these and published data for Jamaican and Hispaniolan anoles, an examination is made of predictions based on definitions of ecomorphs by Williams (1972, 1983). Grass-bush and trunk-crown anoles exhibited higher movement rates than trunk-ground anoles. Data for other radiations agree and support a prediction of relatively high movement rates for twig and trunk ecomorphs. All the species studied were ambush foragers and all used the head-down survey posture, indicating phylogenetic stability of these traits. Arboreal species adopted survey posture in about 75% of observations, and grass-bush species used it when on elevated perches. Rates of foraging movements increased as perch height decreased in grass-bush ecomorphs owing to visual obstruction by vegetation limiting the scanning area close to the ground. A similar relationship occurred unexpectedly in a trunk-crown II species, A. stratulus, whereas movement increased marginally with perch height in a trunk-crown I species, A. evermanni. Perch height and movement rates were unrelated in three trunk-ground species. Movements per minute and per cent time moving were highly correlated among species owing to the brevity of individual movements. Data from other Greater Antillean radiations are needed to separate the effects of ecology and phylogeny on anole foraging.

Age Differences in Wing Loading and Other Aerodynamic Characteristics of Red-tailed Hawks

Abstract We examined age differences in wing loading, aspect ratio, wing span, and tail area in a sample of 117 Red-tailed Hawks (Buteo jamaicensis) captured at the Cedar Grove Ornithological Station, Wisconsin, during 1979–1987. Adults had significantly wider wings, lower aspect ratios, shorter tails, and smaller tail surface areas than juveniles. Red-tailed Hawks showed fewer age differences in aerodynamic characteristics than Sharp-shinned Hawks (Accipiter striatus), probably because of differences between the two species in the pursuit and capture of prey. Sharp-shinned Hawks take birds from above ground or after a brief chase, often in dense vegetation. Sharp-shinned Hawks require more aerial agility (ability to make rapid twists and turns) than is necessary for Red-tailed Hawks, which capture prey on the ground, usually after a glide or flight from an elevated perch.

Interpopulation Variation in the Social Organization of Female Collared Lizards, Crotaphytus collaris

AbstractWe tested the hypotheses that levels of intrasexual aggression and the social structure among neighboring females differed in two central Oklahoma populations of collared lizards, Crotaphytus collaris, and examined the extent to which variation in aggression might be related to differences in the availability of arthropods, elevated perches used by females to scan for prey, and crawlspace refugia. Because both the costs of aggression and access to resources may influence female fitness, we also compared growth and survival rates and the number of clutches produced. At Morningside Farms Ranch (MS), lizards occupied naturally‐formed sandstone washes with naturally‐sculpted irregular topographies, whereas they inhabited homogenous fields of boulders used to construct flood control spillways at the Arcadia Lake Dam (AL). The frequency of intrasexual aggression was markedly higher at MS, and groups of MS females had social hierarchies structured by size and age with older females defending territories, whereas no such social structure was apparent at AL. Moreover, experimental removal of individuals from female groups resulted in more pronounced changes by the remaining females at MS than at AL. Elevated perches and crawlspace refugia were much less abundant at MS. Arthropod availability was similar at the two sites, but at AL arthropods were clustered near the edges of rock patches where elevated perches overlooking adjacent grassy areas were particularly abundant. MS females showed lower rates of survival, and growth during the first year (when growth is highest) than AL females, whereas the number of clutches produced by females at the two sites was similar. Our results suggest that variation in the availability of perch rocks may have resulted in differences in female social structure at the two sites, and relaxed intrasexual competition for perches may have resulted in higher female fitness at AL.

More bang for your buck: the effect of caller position, habitat and chorus noise on the efficiency of calling in the spring peeper

Many animals use acoustic signals as a means of intra- and inter-specific communication. For example, male anuran amphibians produce advertisement calls to attract females for breeding, and as a territorial signal. The production of acoustic signals can be energetically costly, and the distance over which a signal is effective depends on a range of variables including the location of the caller and receiver, ambient conditions and the habitat through which the sound travels. This paper presents a spatially explicit model of the propagation of an anuran advertisement call across a landscape, using the example of the northern spring peeper Pseudacris crucifer crucifer. The model is used to investigate (a) the effect of habitat, caller position and chorus noise on the effective distance of a call with a frequency of approximately 3 kHz; and (b) the energetics and efficiency of calling at different intensities and from different locations in the landscape. Calling next to still water or from an elevated perch increases, while calling in a chorus decreases, the distance over which a female can distinguish an individual male's call. For a given call intensity and calling rate, a male spring peeper will get the greatest “bang for its energetic buck” if it calls next to still water in the absence of chorus noise. However, when a chorus of spring peepers is gathered at a pond, calling from an elevated position away from the pond (and the chorus noise) will maximise the effective distance of an individual call, although this may entail other costs. The model presented here is the first realistic, interactive mathematical model of the propagation of animal sounds across a landscape, and uses a gis interface to display the effect of habitat and caller position on animal communication. It has applications for both research and teaching, and a copy can be obtained free of charge by contacting the author.

The prevalence of feather pecking and development in commercial flocks of laying hens

Feather pecking and cannibalism remain serious problems when laying hens are intensely farmed, but there is not much data on the true prevalence of feather pecking under commercial conditions. A recent epidemiological survey estimated it to be 37.5%. To verify this value we collected data on the occurrence of feather pecking by means of direct observations. Twenty-five rearing flocks on commercial poultry farms were included in the study. Observations were made in weeks 5, 14, 20, 32 and 50. Additionally plumage condition was evaluated and mortality and egg production were recorded. The observations revealed that 40.0% of all flocks had developed considerable frequencies of feather pecking (>30 feather pecking interactions per 30 individuals per 30 min) by week 5 and by week 14 this had risen to 77.3%. The frequency of feather pecking interactions increased significantly between weeks 5 and 14, then there was a significant decrease at week 20 and the level remained the same in week 32. Feather pecking became more damaging with increased frequency and with increasing age of the birds. Each week the relative amount of severe feather pecking was positively correlated to the overall frequency of feather pecking in a flock and the regression coefficient for these two measurements increased steadily from weeks 5 to 32. Very little damage to the plumage was recorded before week 20, but thereafter damage increased significantly in weeks 32 and 50. Feather pecking did not influence mortality, but egg production was negatively affected in week 32. We conclude that more attention should be paid to the development of feather pecking during the rearing of laying hen chicks. Its consequences are not immediately evident, but frequencies of feather pecking remain high as the birds get older, with damage to the plumage increasing and egg production may be reduced. Therefore, all known risk factors such as a lack of access to elevated perches, high density or bad air quality should be controlled in order to prevent development of feather pecking during the rearing of laying hen chicks.

Are genetic differences in foraging behaviour of laying hen chicks paralleled by hybrid-specific differences in feather pecking?

Feather pecking is a behavioural disorder in laying hens which consists of pecking the feathers of conspecifics, causing feather damage or even injuries to the skin. Its development can be explained by redirection of foraging behaviour. While the occurrence of feather pecking strongly depends on the kind of housing condition, it is also known that there are strain differences in the tendency to feather peck. From the inverse relation between feather pecking and foraging behaviour found earlier, we hypothesised that genetically determined differences in foraging behaviour could be responsible for the observed differences in feather pecking between strains. In a first experiment we tested whether there are differences in the foraging behaviour of two hybrids. As hybrids, we used Lohman selected leghorn (LSL) and Dekalb; eight groups of 20 1-day old chicks each. They were kept in enriched pens (265 cm×90 cm) with a litter area (200 cm×90 cm) consisting of wood-shavings, chaff, straw, polystyrene blocks, sand area (65 cm×90 cm) and elevated perches. Behavioural observations were carried out in week 4. In a subsequent experiment with the same birds we tested how the foraging behaviour of the two hybrids differed when housing conditions were changed from enriched to restricted and to what extent they developed feather pecking. A 2×2 factorial design with hybrid (LSL, Dekalb) and housing condition (restricted, enriched) as factors and with four replicates of each factor combination was used. Half of the pens of each hybrid were changed from enriched to restricted housing conditions by covering the litter area with slats. Behavioural observations were carried out in weeks 5 and 6. In experiment 1, LSL and Dekalb spent the same amount of time foraging, but Dekalb spent significantly more of that time with pecking and hacking at the polystyrene blocks. On the other hand, LSL spent significantly more time at the feeding troughs and rested significantly less than Dekalb. In the restricted environment of experiment 2, again, the total foraging time did not differ between hybrids, but LSL chicks spent significantly less time scratching, while Dekalb spent significantly more time moving. Both hybrids developed feather pecking but LSL showed significantly higher rates than Dekalb. Our results demonstrate genetic differences in the foraging behaviour and in the way hybrids cope with the change in housing condition from enriched to an environment that is restricted in relation to foraging possibilities. We conclude that the results support the hypothesis put forward that genetic differences in foraging behaviour could be the basis for the genetic influence in the development of feather pecking.

Hunting mode and success of African PeregrinesFalco peregrinus minor,does nesting habitat quality affect foraging efficiency?

Peregrine FalconFalco peregrmushunting behaviour was studied at nest‐sites in three areas of South Africa over eight years. In Africa, resident Peregrines are mostly restricted to high cliffs, possibly because these structures provide optimal conditions for hunting. This hypothesis is examined in terms of the influence of nest‐site quality, particularly cliff height, on foraging efficiency. Foraging mode varied considerably between sites, and males foraged more actively than females but there was little variation in the design of hunts between sexes, seasons or study areas. Individually, Peregrines spent 30–50% of the day on or near the nest cliff. On average, about 0.5 hunts were recorded per hour of observation. Foraging mode was not correlated with cliff height or elevation above the surrounding terrain, but Peregrine pairs occupying higher cliffs achieved greater hunting success rates. Most hunts were initiated from elevated perches on the nest cliff, and perch hunts were more successful than strikes made from the air. Success was highest in strikes at doves and small passerines, and over habitats with moderate cover. The height difference between Peregrine and prey at the start of a hunt positively and significantly affected hunting success. Overall, Peregrines were relatively sedentary and made extensive use of the nesting habitat as a foraging area. High nest cliffs contributed to foraging success by providing perch‐hunting falcons with an effective height advantage over their prey.

Analysis of risk factors for the occurrence of feather pecking in laying hen growers

1. Potential risk factors for the occurrence of feather pecking in laying hen growers raised under commercial conditions were investigated on Swiss farms with more than 500 rearing places. On-farm interviews were conducted on a sample of 64 flocks which represented 42.6% of all farms concerned. 2. All variables considered were dichotomised and their univariate correlation with the occurrence of feather pecking was tested for significance at P<0 20 using chi 2 tests. Logistic regression with backward elimination was then used with the significant variables to identify the potentially most important factors influencing feather pecking. These variables included stocking density, light intensity, intensity of care, access to elevated perches, access to a roofed and littered outdoor area ('bad weather run'), time of access to the feeding facilities of the housing system, stocking density in the restricted area at the beginning of the rearing period, additional open feeding areas in the beginning and air quality. 3. The final model contained stocking density and access to elevated perches as significant factors (P<0.05). Flocks kept in high density (10 birds per m2) and with no access to elevated perches were 6.4 (95% Confidence interval 1.7 to 24.2) and 4.0 (95% Confidence interval 1.2 to 12.9) times more likely to be affected by feather pecking, respectively. 4. The study identified 2 risk factors for the occurrence of feather pecking in flocks of laying hen growers reared under commercial conditions. It is concluded that in order to reduce feather pecking chicks should be reared at low density and with access to elevated perches.

Laying hens in large flocks in a perchery system: Influence of stocking density on location, use of resources and behaviour

1. ISA Brown laying hens (3000) were housed in a perchery in 10 pens, each with 300 birds. The pens varied in size to produce 4 different stocking densities: 9.9 birds/m2 (n =3), 13.5/m2 (n =2), 16.0/m2 (n =2) and 19.0/m2 (n =3). Observations began at 20 weeks of age and continued until 69 weeks to establish the spatial distribution of the birds, usage of the different resources and the expression of behaviour. 2. Overall, birds spent most time on the perch frame (47%), litter area (23%), slatted floor (17%) and nestbox area (9%). 3. There was no effect of density on the proportion of birds observed on the slatted floor or on the elevated perches but as density increased the proportion on the littered area decreased. 4. Space usage was determined vertically, horizontally and longitudinally . Individual birds were seen to use about 80% of the pen volume available to them. This value was similar for all densities and showed that individuals did not have separate home ranges. 5. Fewer vertical movements were made within the main perch frame at the upper than at the lower levels but movements between the perches of the main frame and the nestbox rails were relatively frequent. This may help birds move up and down through the main frame. 6. Behaviours which decreased in incidence with crowding included moving, foraging and dust-bathing. Behaviours which increased with crowding included standing. Behaviours which were unaffected included resting, preening, prelaying behaviour, comfort behaviour and the minor behaviours. 7. The proportion of birds engaged in feeding and drinking was unaffected by density, except each time the chain feeders (which operated intermittently) ran more hens were seen feeding at the lower densities. This suggests that food delivery stimulated feeding behaviour; there may have been some restriction at the higher densities on birds feeding when and where they wanted. 8. Stocking density had no effect on the frequency of agonistic interactions: threats, lunges, comb/head pecks, chases and fights. 9. The incidence of damaging pecking was low and not density dependent. 10. Increasing density within the range investigated inhibited the expression of a number of behaviours and limited the use of specific resources: bird welfare at 19 birds/m2 may have been very slightly impaired.

Notes on the ecology of a suburban population of Rainbow lizards in coastal Kenya

Aspects of the ecology of a suburban population of rainbow lizards, Agama agama Linnaeus 1758, have been studied in Malindi, a coastal locality of SE Kenya. Four different family groups were monitored on a wall transect 120 m long. Each group constituted a dominant male (i.e. a brightly coloured and aggressive individual) and three to four adult females, but in one of the studied groups a subordinate male was also seen. Both sexes were active in the morning, and peak activity fell between 10.00 and 11.30 hours. Dominant males used elevated perches significantly more often than subordinate males and females. The diet consisted of terrestrial arthropods, and most of the prey eaten were beetles (6–8 mm long). The foraging strategy used by rainbow lizards was to eat small insects at very short time intervals. The lizards used sit‐and‐wait foraging, remaining motionless until the prey was &lt;5 cm away. The rainbow lizards studied did not feed upon plant material.

Variation in Time and Energy Budgets of Breeding Wheatears

Abstract We examined the sources of variation in time allocation of males and females of the wheatear (Oenanthe oenanthe) on the island of Öland, South Sweden, throughout the breeding season. We quantified rates of prey capture attempts and specified foraging methods used. From respirometric measurements of basal metabolic rate and temperature-dependent metabolism on captive wheatears, and after having made certain assumptions abour the costs of different activities, we estimated the energy budgets of both sexes during the different reproductive phases. Males and females differed in their time allocation and foraging rates during prelaying, laying, and incubation, but not while feeding grown nestlings. During prelaying and laying, females foraged at higher rates than males; they also perched less often, gleaned more on the ground, and flew less. Although incubation was the least costly phase for females because of their low activity, high foraging rates yet indicated that this phase may represent an energetic bottleneck as a result of restrictions on foraging time. After incubation, females switched from foraging mostly on the ground during early breeding phases to hunting from elevated perches during later breeding phases. The shift in foraging behavior corresponds to the drastic changes in time allocation. Relatively high daily energy expenditures (DEE) by brooding females coupled with low foraging rates may explain the observed posthatching body mass losses. In both sexes, high required energy acquisition rates when feeding large nestlings indicate that parent wheatears then may encounter another energetic bottleneck. Postfledging was the least costly phase because, compared with the period of feeding nestlings, there were reduced thermostatic costs and a marked drop in flight time. Males and females had similar DEEs during prelaying, laying and nestling feeding, but females had lower needs during incubation. The elective components of energy budgets during nestling feeding, as well as the estimated sum of the elective components throughout the season, were 12% higher for males than for females. The elective components of the energy budgets varied more than the obligatory components (basal + thermoregulation), especially in females, and were more important in determining the variation of DEE throughout the breeding season. A validation study with doubly labeled water indicated that the energy budget model used was accurate enough for comparisons between sexes or breeding phases, but not for measuring individual variation.

Some Determinants of the Mating System in a Population of Painted Reed Frogs (Hyperolius Marmoratus)

AbstractHyperolius marmoratus shares its breeding site with 12 synchronously breeding species. Males call from elevated perches to attract females. Observations of captive populations suggest that males may adopt alternative mating strategies when chorus densities are high. Similar strategies were not observed in natural choruses. The operational sex ratio (OSR) was always male-biased and also highly variable. Mating was polygynous, only 25% of the male population actually mated. Females mated either once or twice. Variance in mating success was much greater among males, an obvious consequence of a skewed OSR. Female choice was probably not a causal factor because male mating success was correlated with neither size nor age. Size-based variation in the male advertisement call does exist, but females cannot exploit this potential vocal cue because of their impaired discriminatory ability in a complex sonic environment and the potential risk of mismating. Although the mating system may best be described as lek-like, with males forming organised choruses through competitive interactions, the variance in male mating success is probably a consequence of stochastic factors.

The influence of simulated aquatic macrophytes on the zooplankton consumption rate of juvenile roach, Rutilus rutilus, rudd, Scardinius erythrophthalmus, and perch, Perca fluviatilis

Laboratory experiments showed that, of zooplanktivorous roach, rudd and perch, in the absence of any environmental structure roach were the most efficient feeders, but high densities of simulated submerged marcrophytes elevated perch to this position; rudd matched the performances of perch and roach only at intermediate structure densities. These changes in efficiency rankings with increased structure were the result of overall decreases in the performances of roach and rudd. Simulated water lilies and emergent reeds had their own influences on consumption rate. These effects were largely mediated through relationships between structure density and swimming speed; roach and rudd, not perch, showed reduced swimming speeds in the more structured environments. Observations of the routine behaviour of the fish suggest that their assessment of predation risk may be an important factor in determining their activity level and hence foraging strategy.

Thermal Soaring Compared in Three Dissimilar Tropical Bird Species, Fregata Magnificens, Pelecanus Occidentals and Coragyps Atratus

ABSTRACT All three species were observed in straight flight, and circling in thermals, from Flamenco Island, Panama. Measurements were made by or-nithodolite, an instrument which records a series of timed, threedimensional position estimates, from which speeds, circle diameters and rates of climb can be calculated. Mean lift coefficients in straight glides ranged from 0·72 to 0·84, except in slope soaring, where a mean of 1·6 was recorded for both the frigatebird and black vulture. Mean circling radii were proportional to wing loading, and varied from 12·0 m for the frigatebird to 18·0 m for the pelican. Mean rates of climb ranged from 0·40ms−1 for the black vulture to 0·57ms−1 for the pelican. All species showed mean circling lift coefficients between 1·33 and 1·45, and angles of bank between 22·9° and 24·7°. It is argued that the frigatebird is adapted to stay airborne continuously, day and night, for extended periods, by exploiting thermals over the sea under trade wind cumulus clouds. The low wing loading is seen as an adaptation to circling in narrow thermals, and the low disc loading as an adaptation giving low minimum power, when flapping cannot be avoided. Take-off appears to be possible only by dropping from an elevated perch, not from the ground or water surface. The low aspect-ratio, tip-slotted wings of the black vulture are certainly less efficient for soaring, but appear to be better for upward take-off from the ground. The pelican also has tip-slotted wings. Although its aspect ratio is higher, it is still capable of taking off from a level water surface.

Brood Parasite and Host Coevolution: Interactions between Shiny Cowbirds and Two Species of Meadowlarks

I studied host-parasite interactions of the shiny cowbird and two species of meadowlarks on the Argentine pampas. The greater red-breasted meadowlark (Sturnella loyca) suffered a high rate of parasitism (23 of 24 nests) while S. defilippii appeared to escape parasitism (0 of 11 nests). Cowbirds visiting the study area associated preferentially with S. loyca, and approached decoys more often when S. loyca song was broadcast. The S. loyca is dependent on elevated perches and usually nests near them, while S. defilippii does not require such perches and does not nest near them. The perches near S. loyca nests apparently facilitated nest-finding by cowbirds. Female S. defilippii were more surreptitious than S. loyca females during nest-building, and although S. loyca females interrupted nest building when cowbirds arrived, the cowbirds were usually more patient and succeeded in finding nearly all of the nests that I found. The shiny cowbird can benefit by focusing attention on S. loyca since that species is numerous, conspicuous, nests near elevated perches, and is less careful in nest building (compared with its more numerous and equally conspicuous congener). The close association of S. loyca male and female assure that a cowbird approaching a singing male S. loyca will be near the female. These factors render S. loyca a host with high primary suitability. Moreover, it is clearly not a rejector nor deserter species; hence it has good secondary suitability. It is not certain if it ever raises cowbirds to independence, but in this study I found no evidence that any cowbirds fledged, and I found many fledged meadowlark broods without cowbirds. I conclude that it has low ultimate suitability for the shiny cowbird. Although S. defilippii is numerous, its nests are not near perches and the male and female are not found close together; hence it has low primary suitability. I have no evidence that it is either a rejector or deserter, but experiments should be done to clarify these points. There is no evidence on the ultimate suitability of S. defilippii as a host, except the lack of reports of S. defilippii feeding fledgling cowbirds. Since there are few S. loyca-reared cowbirds (if any) a system of foster specificity does not account for the responses of cowbirds to S. loyca. Rather it seems likely that individual cowbirds learn of S. loyca's primary suitability and focus attention on it for that reason. Although ultimately selection should act against birds that lay in S. loyca nests, the high primary suitability actually allows S. loyca to "compete" for cowbird eggs against other hosts. A system based on host-recognition through imprinting is perhaps ideal since the fact that one has matured is prima facie evidence that one has been raised by an ultimately suitable host, and such a system offers protection against the kind of errors involved in choosing a host with high primary but low ultimate suitability. The use of song as a cue in distinguishing hosts allows cowbirds to benefit from the fact that hosts sing more just prior to the onset of incubation, the most propitious time for nest discovery. The parasite's time investment in nest-finding must be adequately repayed, and focusing attention on a host with low primary suitability means that cowbirds will not find enough nests in one season. Only if one could assure gaining a host with high secondary and/or ultimate suitability would excess nest-finding time be adequately repayed.

BEHAVIOUR OF WOODLAND KINGFISHERS IN GHANA

Summary Greig-Smith, P. W. 1978. Behaviour of Woodland Kingfishers in Ghana. Ostrich, 49:67-75. The behaviour of Woodland Kingfishers Halcyon senegalensis was studied during the breeding season. Inactive postures were dependent on alertness, perch height, and time of day. Prey was mainly grasshoppers, captured by diving from elevated perches. Breeding territories were near water, and were maintained by a long-range vocal display, a short-range visual display and attacks on intruders. Other bird species were also attacked. Courtship involved “duets”, display flights, and allofeeding. A late wet season in 1974 apparently caused delayed migration, and postponement of all breeding behaviour except inspection of nest-holes.