Chorusing Behaviour in the Lusitanian Toadfish: Should I Match My Neighbours' Calling Rate?

Choruses have been described mostly in birds, anurans and insects but have been poorly studied in fish. Research in batrachoidid (toadfishes) species suggest vocal facilitation among neighbouring males, but whether chorusing fish present more complex interactions is unknown. In this study, we test the hypothesis that chorusing fish males compete actively to increase attractiveness to females. We first describe vocal interactions in natural choruses of Lusitanian toadfish males. Our analysis found positive correlations between the calling rates of neighbouring males in several occasions. However, we also found that males that showed an overall low vocal activity throughout the observation period exhibited peaks of increased calling activity when neighbours decreased their calling rate, suggesting an opportunistic maximisation of attractiveness. We further test with playback experiments how toadfish males adjust calling activity relative to their neighbours'. We observed that males silent at the time of the playbacks but who had an overall high vocal performance tended to start calling when exposed to playbacks in contrast to low‐activity males. Playback experiments further showed that males initially calling at a high rate adjust their calling rate according to the neighbour's vocal activity level, that is, they increased calling rate when exposed to a high calling rate and decreased it when confronted with a low calling rate. However, males calling at a low rate did not significantly alter their calling rate when presented with a low (similar) or higher calling rate, probably due to temporary physiological and/or ecological constraints. We argue that Lusitanian toadfish males tend to optimise calling effort in relation to their neighbours when they are actively advertising. Further studies are necessary to better understand vocal behaviour with increased chorus size.     

Territoriality and Male Mating Success in the Dart-poison Frog,Epipedobates femoralis (Dendrobatidae,Anura)

The social and reproductive behaviour of the dart-poison frog, Epipedobates femoralis, was studied in Amazonian Peru for 14 months. Males defended territories with advertisement calls and, ultimately, fighting. Territory size ranged from 0.25 to 26 m² and was positively correlated with duration of residence and calling activity of the owner. Females were not territorial and were never attacked when approaching calling males. Males and females only mated once and females sampled calling males before mating. Male mating success was closely correlated with territory size and calling activity. No correlation was found between male body size and mating success. Territories provide residents with sufficient space for mate attraction and reproduction without interference from rivals. Since territory size is dependent on calling activity which involves high energetic costs, it is suggested that territory size reveals male quality.     

Pairing strategies and mate choice in female robins Erithacus rubecula

Female European robins (Erithacus rubecula) adopted three different pairing strategies. These were, in order of frequency: moving on to a male's territory; fusing her territory with that of a neighbouring male; and being joined by a male on her territory. Although females were not free to choose between strategies during a particular season, individuals frequently changed strategy between different years. Their behaviour suggested that they were exercising mate choice, although the scope for such choice was limited by a strong tendency for a female to pair in areas where she had lived previously (her ‘Familiar Areas’). Males with large territories were more likely to pair and tended to pair earlier than those defending small territories. Female pairing strategy was also correlated with the area of their own territory. Although it is considered likely that some unidentified confounding variable was responsible for at least part of these relationships, possible causal explanations involving territory size are discussed. These include mate choice and a random settlement model. However the simplest explanation for the advantage enjoyed by males on large territories is that their territories were more likely to overlap with females' Familiar Areas.     

Home range and territory of the Sardinian Warbler Sylvia melanocephala in Mediterranean shrubland

Capsule Singing territories were well separated.

Aims To examine the spatial distribution of Sardinian Warbler males during the breeding period in Mediterranean shrubland and, specifically, their territories, home ranges and spatial overlaps.

Methods We studied a 12-ha plot of Mediterranean shrubland in the 1997 to 1999 breeding seasons. Sardinian Warblers were captured using mist-nets, colour-ringed and their territories mapped. In 1999, seven breeding males were radiotracked in order to map home ranges.

Results The Sardinian Warbler had an average of 7.3 breeding pairs/10 ha in the study plot. The mean territory size was 8779 m² and the mean home range was 22 321 m². A positive relationship was found between the area of the home range and singing territory. Home ranges of males born in 1998 were about half the size of those of the oldest males. Paired males who moved with a female had smaller home ranges than those that were either unpaired or whose mate was incubating. The degree of home range overlap was high with some overlap between neighbouring territories. The estimate of home range area increased by 10% when the information generated by a mapping method was added and the estimated territory area increased by 31% when data generated by radiotracking were added. Transmitters remained attached to birds for an average of 9.63 ± 3.46 days (mean ± se).

Conclusions Singing territories were segregated to a considerable degree. In contrast, the wide overlaps among home ranges was best explained by the presence of food resources that the males exploit at the same time and also by the search for extra-pair copulation in nearby territories. We consider radiotracking in this species to be feasible and valid, with no evidence of negative effects on activity levels, weight or mortality.     

Song matching in a long-lived,sedentary bird with a low song rate: The importance of song type,song duration and intrusion

Territorial songbirds often match the song features or singing patterns of rivals, commonly as an aggressive signal. Most studies of song matching have been on Northern Hemisphere species with short lifespans and high song rates, but vocal matching is predicted to be affected both by longevity and territorial stability. We studied song matching in males of the white-browed scrubwren, Sericornis frontalis, a long-lived, sedentary, territorial Australian songbird. We quantified natural song rate and diversity, and then conducted three playback experiments to test: (a) whether males match by song type; (b) how they respond physically and vocally to territorial intrusion; and (c) whether they match by song length, and use it as an agonistic signal. Males naturally had very low song rates, singing on average less than three times per hour, and moderate repertoires, with an estimated mean of 17.5 song types for individual males. Males did not engage in extended counter-singing bouts. The first experiment showed that males matched the song type of immediate neighbours almost 90% of the time, if that type was in their repertoire. The remaining experiments revealed that song-type matching was an aggressive signal; males responded more aggressively to, and were more likely to match, playback simulating a neighbour's territorial intrusion than song from their shared boundary. Males did not match songs by length, but they produced longer songs after simulated intrusion. Males also responded more aggressively to playback of longer songs that simulated intrusion, but less aggressively to longer songs from the territory boundary. Overall, we show that sedentary, long-lived songbirds with low song rates, can use song-type matching as an aggressive signal to communicate with neighbours and intruders. Song length had a different role in communication, possibly related to individual quality or territory ownership.     

Disruption of Dear Enemy Recognition Among Neighboring Males by Female Leon Springs pupfish, Cyprinodon bovinus

Males defending territories often settle into adjacent areas, sharing a common border that is maintained by a reduced level of aggression known as dear enemy recognition. While social conditions may affect the dear enemy relationship among males, what role females play, if any, is unclear. In a field study of the highly promiscuous Leon Springs pupfish, Cyprinodon bovinus, we asked whether females influenced this relationship of neighbors to their advantage. We observed 16 territorial residents, mapping the precise location of each male's behaviors within its territory. Resident males engaged in less aggression against neighbors compared with intruders, and neighbors intruded less deeply into the residents’ territories than intruders. Despite this locality restriction, neighbors were responsible for as many spawning interruptions as intruders. Females did not spawn randomly in the males’ territories, nor did they spawn near territory centers where aggression was low. Rather, females were more likely to settle and spawn in the outer half of the territories where competition among males was highest. When a neighbor entered a resident's territory to interrupt a spawn, the female was more likely to leave the resident's territory for the neighbor's than to remain. These observations suggest that the female used the intrusion by the neighbor to engage the resident and interrupt the spawn as a measure of this male's quality and that, while neighboring males benefit from the presence of dear enemy recognition, females benefit from its disruption.     

Territorial songs indicate male quality in the sac-winged bat Saccopteryx bilineata (Chiroptera, Emballonuridae)

Defense of territories in many animal species involves the advertisementof territory holder quality by acoustic signaling. In the sac-wingedbat Saccopteryx bilineata, males engage in territorial countersingingwhen reoccupying their day-roost territories in the morningand in the evening before abandoning the roost for the night.Females roost mainly in male territories, and territory holdersare reproductively more successful than nonterritorial males.In territorial songs of male S. bilineata, we distinguished6 syllable types and parameterized their acoustic properties.The analysis of 11 microsatellite loci allowed assignments ofjuveniles to their parents. Males had a higher reproductivesuccess both when they uttered more territorial songs per dayand when their long buzz syllables had a lower end frequencyof the fundamental harmonic. Long buzzes had a harsh qualitydue to a pulsation of the fundamental frequency at the syllableonset and also had the highest sound pressure level of all syllabletypes in most territorial songs. Territorial songs and especiallylong buzz syllables are thus likely to advertise territory holderquality and competitive ability.     

Should I stay or should I go? Territory settlement decisions in male Corncrakes Crex crex

Capsule: Corncrake Crex crex males shift their territories and change habitat preferences across the breeding season as a consequence of anthropogenic pressure and/or to enhance the chances of reproduction through sequential polygamy.

Aims: To examine how habitat structure changed during the breeding season, whether Corncrake males responded to those changes and which habitat features were crucial when males settled and occupied territories.

Methods: Calling male Corncrakes were surveyed six times during the breeding season. In each location where a calling male was recorded, the habitat and vegetation structure was described from one to three times during the season.

Results: Corncrake males avoided extremely wet and extremely dry habitats, whereas large sedge and reed communities were much more preferred. There were significant seasonal changes in the density of vegetation and moisture content. Males were more sedentary at the beginning of the breeding season. Males significantly changed habitat preferences in short-periods of time. However, none of the habitat-related features explained whether males stayed or left the territory.

Conclusion: Corncrakes shift their territories during the breeding season in response to anthropogenic pressure (agricultural activity) as well as changes in water levels during the year. However, territorial shifts within seasons might also be caused by the appearance of fertile females in different habitats at different stages of the breeding season.     

The role of territory settlement,individual quality,and nesting initiation on productivity of Bell's vireos Vireo bellii bellii

Variation in habitat quality among territories within a heterogeneous patch should influence reproductive success of territory owners. Further, territory settlement order following an ideal despotic distribution (IDD) should predict the fitness of occupants if territory selection is adaptive. We recorded settlement order and monitored nests in territories occupied by individually marked Bell's vireos Vireo bellii bellii across a range of shrubland habitats in central Missouri, USA. We used an information theoretic approach to evaluate multiple hypotheses regarding the relationship between territory settlement order and seasonal territory productivity (productivity), which we define as the number of young fledged from all nest attempts in a territory. Territory settlement order and arrival date were not analogous and later arriving males displaced early settlers in 13 of 49 territories. Settlement order and lay date together were the best predictors of a territory's productivity; productivity decreased 2.08 young from earliest to latest settlement rank and lay date. Males that defended the same territory in successive years occupied territories with earlier settlement dates, but we found little evidence that age or prior ownership influenced productivity. Territory selection by male Bell's vireos was adaptive because males preferred to settle in territories that had high seasonal offspring production, but even though settlement rank was linked to territory quality, high productivity was only realized on high quality territory when also linked to early nest initiation date. While settlement rank was related to territory quality, obtaining a high quality territory had to be combined with early nest initiation to maximize productivity. We found support for the IDD hypothesis because the highest quality territories, (i.e. most productive), were settled earlier. Research that identifies high quality habitat by linking individual fitness with habitat characteristics may elucidate the importance of habitat quality, individual experience and temporal factors to productivity of Bell's vireos.     

The first UK survey and population estimate of breeding Snow Bunting Plectrophenax nivalis

Capsule: The first national survey for Snow Bunting Plectrophenax nivalis in the UK was carried out in 2011 and estimated the breeding population at 60 territories (95% confidence intervals?=?48–83).

Aims: To estimate breeding population size for Snow Buntings in the UK by surveying all sites with a history of breeding season occupation.

Methods: Surveys were carried out in June 2011 to detect males on territory at sites where Snow Bunting had been recorded during the breeding season since 1970. Each site was visited at least once during the survey period; suitable habitat was searched and vantage point watches were conducted in order to detect singing males. Repeated visits to a sample of sites allowed a correction factor to be calculated in order to account for birds undetected during surveys.

Results: In 2011, the number of Snow Bunting breeding in the UK (including adjusting for imperfect detection) is a minimum of 60 territories (95% CI?=?48–83) using confirmed and probable breeding records of males. A less conservative estimate of 99 territories (95% CI?=?88–114) results from including all records of males in suitable habitat. The vast majority of the population was found in the Cairngorm region, with isolated records in the north and west Highlands.

Conclusion: The results of the 2011 survey are consistent with well-informed estimates of the Snow Bunting population made previously. This work provides a baseline and repeatable fieldwork and analytical methods enabling future change in the population to be quantified more rigorously.     

Determinants of the Mating Success of Polyterritorial Pied Flycatcher Males

Much attention has been paid to the polyterritorial mating system of some passerine birds. Here we report how a male's mating success is related to the behavioral traits of polyterritorial pied flycatcher (Ficedula hypoleuca) males. We found no evidence that the timing of polyterritoriality in relation to egg laying in the primary nest or the singing behavior of males have any influence on mating success. However, results show clearly that male mating success was improved with an increase in the distance between territories up to a distance of about 200–300 m whereupon there was no further enhancement of mating success. This finding is crucial for both the deception hypothesis and female-female aggression hypothesis which have been put forward to explain polyterritorial polygyny. Males who establish a distant second territory seemed to allocate more time to singing there. The association, although weak, between singing activity and distance between territories makes it more difficult for females to use song rate as a cue to discriminate males with a secondary territory far from the primary territory, and these are the males that are least likely to feed the young of a second female. Males who established a second territory late in relation to egg laying in the primary nest did not take over a close second territory as might be predicted from female-female aggression hypothesis.     

Structure of tree vegetation may reduce costs of territory defence in Eurasian Nuthatch Sitta europaea

Capsule In pastured old oak woodland, breeding pairs of Eurasian Nuthatch selected territories with significantly higher densities of trees and cavities.

Aims To define territorial borders that exist within a nuthatch population and to compare densities of trees and cavities between used and non-used parts of their available habitat in order to determine habitat preferences.

Methods The number and location of territories was estimated by mapping the individual positions of colour-ringed birds. We measured habitat characteristics in regular sampling grid (number of trees and number of cavities per 50?×?50?m) during three successive seasons and modelled probability of occurrence of nuthatch territories in the area.

Results Breeding pairs were observed to defend territories of median size between 1.46 and 2.93?ha. These sizes correspond well to high-quality habitat territories for this species. We found that pairs tended to occupy territories with higher densities of trees and cavities. Based on generalized linear mixed-effects model estimates, we found that in pastured oak woodland habitat with density of 60 trees per ha, the estimated probability of occurrence (with 95% confidence interval) of a nuthatch territory was about 96% (83?99). For cavity density, the probability of territory occurrence was about 74% (52?89) at the level of 60 cavities per ha.

Conclusion We suggest that higher tree and cavity densities reduce territory defence costs in the species because birds may use less energy during foraging, predation avoidance and competition for a nest hole.     

Factors constraining the distribution of Golden Eagles Aquila chrysaetos in Scotland

Capsule Between 1992 and 2003 persecution appeared to be the main influential factor.

Aims To utilize temporal changes in the distribution and occupation of Golden Eagle territories in Scotland between the 1992 and 2003 national censuses to assess potential causes of regional and national population trends, by examining spatial associations with a number of potential constraints on the population.

Methods The distribution of occupied and vacant territories in the 1992 and 2003 censuses were entered as layers in a Geographical Information System (GIS), along with boundaries of biogeographical regions (Natural Heritage Zones) for regional analyses. Additional GIS layers were created for potential factors that may constrain the eagle population: the distribution and abundance of persecution incidents, new commercial conifer forests, popular mountains for hillwalkers (as surrogates for recreational activity), and the density of sheep and Red Deer (as surrogates for carrion abundance), drawn from comparable time periods to the national eagle censuses. Analyses then looked for spatial associations between eagle territory status and those constraint factors that may have influenced change in territory status.

Results We found little evidence to suggest that recreational disturbance was influential on the occupation of Golden Eagle territories, although some local effects may have occurred and further analyses are warranted. We could find evidence of only a limited number of territories having being abandoned recently due to the planting of commercial conifer forests. We also rejected the hypothesis that changes in territory occupation between national Golden Eagle censuses were influenced by change in carrion abundance. By contrast, results were consistent with the hypothesis that persecution was influential in the observed change in territory occupation between censuses, so that occupied eagle territories tended to decline where persecution was probably still influential and tended to increase where persecution had probably declined.

Conclusion In accordance with earlier predictions based on models of the demographic influence of persecution, in the central and eastern Highlands where grouse moor management predominates, the eagle population continued to decline to levels where increasingly large areas of suitable habitat are unoccupied by breeding pairs.     

Correlation between male size and territory quality: consequence of male competition or predation susceptibility?

Territory characteristics correlate with male characteristics in several species. This can result from male competition for the best territories, or from males varying in their ability to pay other costs of territoriality, such as predation risk costs. In a population of threespine sticklebacks, Gasterosteus aculeatus , we found the biggest males to defend the biggest territories with a low structural complexity and a high female encounter rate. By experimentally manipulating competition intensity and habitat structure, we show that both male competition and predation exposure influenced the distribution of territories among males. Males increased the size of their territory when a neighbouring male was removed, whereas they reduced their territory when habitat complexity and cover from predators were reduced, with large males reducing their territory size less than smaller males. This suggests that large males occupy large, open territories both because of their superior competitive ability and because of their either lower predation susceptibility or higher risk-taking. Large, open territories were beneficial in mate attraction and male competition and predation exposure therefore biased mating opportunities towards large males. This suggests that cost of territoriality to males may reduce mate choice costs to females by securing that large males are encountered more often than small males, and by providing an additional cue, territory quality, which indicates which males are worth inspecting.     

The influence of age and experience with conspecifics on territorial behavior inDrosophila melanogaster

Drosophila melanogastermales initiated aggressive behavior toward other males and defended territories several hours after they were able to court and mate females. Males that were 3 days or more posteclosion were more successful at holding territories than younger males. Three-day-old males established territories more readily and escalated more often against territory residents than males that were 1 day old. Residents did not usually force young males from territories until they were a few hours posteclosion. The development of territorial behavior was not affected by familiarity or prior exposure to females. Males held in isolation established territories more quickly and behaved more aggressively than males held in groups. Males that previously held territories were more likely to reestablish them after a disturbance.     

Aggression among Lekking Male Fallow Deer (Dama dama): Territory Effects and Relationship with Copulatory Success

We studied the aggressive behavior of territorial male fallow deer (Dama dama) at two leks. Daily number of escalated fights was not correlated with number of matings. A dominance index including all agonistic interactions was weakly correlated with copulatory success; the correlation was stronger when each half of the rut was considered separately. Dominance likely changed over the rut due to fatigue. We ranked lek territories by the number of copulations seen in each. Males that won fights were likely to take over the loser's territory only if it ranked higher than the one they held. Winners were more likely to fight with a third male after defeating an opponent that held a higher-ranking territory than one from a lower-ranking territory. Exposure to attacks by third-party males may be a major cost of fighting. Males appear aware of the relative value of different lek territories, but the frequency of aggression was not scaled to potential fitness benefits, possibly because males seldom fought with opponents they were unlikely to beat. The outcome of interactions on the lek may not always reflect the relative dominance rank of the contestants. Females are unlikely to use the outcome of fights as a direct criterion for mate selection.     

Size-dependent use of territorial space by a rock-dwelling cichlid fish

Territoriality fundamentally influences animal mating systems and patterns of population structure. Although territory ownership is already known to contribute importantly to male reproductive success and the ecological coexistence of African rock-dwelling cichlids, the significance of variation in territory features has received little attention in these fishes. In Lake Malawi, males of Pseudotropheus tropheops "orange chest" defend territories on either of two substrate classes at Harbour Island: flat rock slabs lacking crevices and caves, or structurally complex boulder fields containing cave shelters. Focal watches of this species demonstrated that both territory size and occupancy on either substrate type depend on the size of male residents. Males larger than a threshold size exclusively held the largest and most structurally complex territories. After removal of conspecific residents, more vacant territorial areas on cave-containing substrate were reoccupied by "orange chest" males in full breeding coloration compared to vacant areas on flat substrate. These findings suggest competition among "orange chest" males for complex rocky substrate. Defense of caves was associated with enhanced male courtship rates: the number of caves within a male's territory was a better predictor of courtship activity than was male size or territory area. In addition to territories being crucial for male reproductive success and therefore likely playing a role in sexual selection, male-male competition for caves in rock-dwelling cichlids may be promoted by the ecological advantage of enemy-free space. Smaller "orange chest" males lacking caves tended to move into adjacent boulder fields in the presence of predators, particularly at night. In contrast, males defending caves were more likely to remain on their territories when nocturnal predators were present. The territorial behaviors of P. tropheops "orange chest" that we observed in situ provide an instructive natural framework for testing the roles of substrate and ecology in the mating systems of rock-dwelling cichlid fishes.     

Preliminary study on female choice of mates versus sites in a wrasse, Cirrhilabrus temminckii

Female choice of mates versus sites was studied in a wrasse, Cirrhilabrus temminckii. Males had territories within a restricted area on a rocky slope at which females visited and pair-spawned pelagic gametes. Females visited several males or territories before spawning, suggesting the opportunity of female choice. Of the four characteristics of territorial males examined—body size, ratio of pelvic fin length to body size, courtship, frequency and territory depth—only territory depth was significantly correlated with daily mating success of males. The former three male characters were not related to territory depth. These results suggest that female C. temminckii chooses deep sites rather than specific mates in mating.     

Male Calling Behavior and Female Choice in the Neotropical Treefrog Hyla microcephala

The effect of stimulus call complexity and calling rate on the vocal responses of males and female mate choice was studied in Hyla microcephala in Panama. Males increased the number of notes in their calls in response to increases in stimulus call complexity during both playback of 1 to 8-note advertisement calls and during natural interactions. However, precise matching of the number of notes in stimuli and responses did not occur consistently. Males also increased calling rates if stimuli were presented above prestimulus rates. Two-stimulus choice experiments demonstrated that females prefer both higher calling rates and greater call complexity, indicating that the ways males change their vocal behavior during interactions increases their attractiveness to potential mates. Tests in which the relative intensity of a high and low rate stimulus was varied indicated that females prefer stimuli with higher total sound energy. In a natural chorus, it is likely that females simply approach males giving the most conspicuous calls.     

Assessing breeding success in common woodland birds using a novel method

Capsule Repeated counts of fledged broods can provide a useful estimate of breeding success for most common woodland birds.

Aims To assess the efficacy of comparing fledged-brood survey data with territory mapping using simple mark–recapture analysis techniques to provide an estimate of breeding success for common woodland birds that does not involve finding nests.

Methods Three observers undertook territory mapping surveys of adults, followed by counts of fledged broods four times a week during May–July 2007 in two 15 ha woods each, both in southern England. Using known fledging to maturity periods, these counts were used to calculate daily detection probabilities for broods of ubiquitous species. These enabled fledged brood territory occupancy probabilities (i.e. brood to territory ratios) to be estimated that take account of the possibility that broods were present but missed by surveys.

Results Of the 19 species found in all six woods, mean daily detection probability estimates for fledged broods of 17 species ranged from 0.17 to 0.50 with significant variation between woods for 12 species, but within region/observer for four species. The mean probability of detecting a brood at least once was over 75% using four visits per week and over 50% using two visits. Only for Great Spotted Woodpeckers Dendrocopos major and Garden Warblers Sylvia borin was the fledging period too short and the daily detection probability too low to provide a reasonable estimate of the territory occupancy probability.

Conclusion Daily detection probabilities for fledged broods of most common woodland birds were sufficiently high to enable useable estimates of fledged-brood territory occupancy probabilities to be made based on a survey programme involving two or three visits per week between late May and the end June. The method used may have application as a means of providing a relatively easily derived productivity index for woodland bird monitoring programmes or for research studies.