Interannual assessment of territory quality for male sea otters (Enhydra lutris) in Simpson Bay, Prince William Sound, Alaska

Territory quality and site fidelity were assessed for male sea otters ( Enhydra lutris (L., 1758)) in Simpson Bay, Prince William Sound, Alaska, during the summer months (May–August) from 2003 to 2006. Territory quality was coded with a score of 0–2 for four attributes: territory size, shoreline enclosure, territory accessibility, and number of females observed feeding in each territory. Total quality scores ranged from 0.14 to 1.96 (0.9 ± 0.61, mean ± SD), with the highest quality territories having large areas, moderate to little shoreline enclosure, high accessibility, and many foraging females. A total of 13.1 km2 (62.5%) of Simpson Bay was occupied at least once by a territorial male during the 4-year study, and 7.9 km2 (37.5%) was never occupied by a territorial male. There were 7 ± 2.4 (mean ± SD) territorial males in Simpson Bay each year. Five males maintained territories for two consecutive years, with their respective territories having a 16%–34% overlap between years, indicating that repeat territory holders returned to the same area. The number of territorial sea otters, the size of territories, and whether or not a sea otter was a repeat territory holder did not significantly influence the size or quality of male territories.

Family Structure in the Siberian Jay as Revealed by Microsatellite Analyses

The Siberian Jay (Perisoreus infaustus) lives in resident, territorial family groups outside the breeding season, but does not breed cooperatively. Thereby it offers an opportunity to study the evolution of territorial group living, without confounding effects of reproductive cooperation. During a long-term study in Finland 1974–2000, we observed Siberian Jay group composition in autumn. Using microsatellite analysis based on feather or blood samples we clarified kin relations within the groups. We found that out of 311 groups that included at least one more individual than the territory holders, 74% were nuclear families, including breeding birds and 1–3 retained offspring. However, 26% of the groups were not families, but consisted of pairs accompanied only by individuals that were not their offspring. According to extensive pedigrees we found that 70% of the 82 immatures associated with a nonparent pair were not related to either territory holder. Of these 82 immatures, 91% were associated with pairs that had no offspring on their own, suggesting that they were failed breeders or newly established pairs. The composition of groups was mostly unchanged during the observation period within each season, regardless of kinship. Previous studies have reported apparent nepotism between parents and retained offspring in the Siberian Jay, and a high degree of aggression toward nonoffspring, so we did not expect to find such high frequency and remarkable within-season stability of nonfamily groups. These observations suggest that there are important fitness benefits to gain from territoriality and group living, regardless of kinship. Estructura Familiar en Perisoreus infaustus Determinada Mediante Análisis de Microsatélites Resumen. Los individuos de la especie Perisoreus infaustus viven en grupos familiares residentes que son territoriales durante la época reproductiva, pero no exhiben cría cooperativa. Así, esta especie ofrece la oportunidad de estudiar la evolución del sistema de vida en grupos territoriales sin los efectos de la cooperación reproductiva. Observamos la composición de grupos de P. infaustus en el otoño durante un estudio a largo plazo en Finlandia (1974–2000), y con base en muestras de plumas o sangre, clarificamos las relaciones de parentesco al interior de los grupos mediante análisis de microsatélites. Encontramos que de 311 grupos que incluían al menos un individuo adicional a los dueños del territorio, el 74% eran núcleos familiares, incluyendo aves reproductivas y 1–3 crías. Sin embargo, el 26% de los grupos no correspondían a familias, sino que consistían de parejas acompañadas sólo por individuos que no eran sus crías. Utilizando pedigríes detallados, encontramos que el 70% de los 82 inmaduros asociados con una pareja no parental no estaban relacionados con ninguno de los dueños del territorio. De esos 82 inmaduros, el 91% estuvieron asociados con parejas que no tenían crías propias, lo que sugiere que habían tenido intentos de reproducción fallidos o que se habían establecido recientemente. La composición de los grupos se mantuvo casi constante durante el período de observación de cada estación, independientemente del grado de parentesco. Estudios previos habían reportado un aparente nepotismo entre parentales y sus crías y un alto grado de agresividad hacia individuos que no eran sus crías en P. infaustus, por lo que no esperábamos una frecuencia tan alta de grupos no familiares, ni la marcada estabilidad de éstos. Estas observaciones sugieren que la territorialidad y la vida en grupo proveen beneficios importantes de adecuación biológica, independientemente del grado de parentesco.

Risks of fighting in relation to age and territory holding in fallow deer

Detailed analysis of the fighting and sparring behaviour of male fallow deer (Dama dama) shows that the peculiar palms of their antlers play a role in normal fighting and sparring. Analysis of the risks involved in the different fighting techniques (according to the force and torque, and the bending stress produced in the antlers) shows a tendency for the best endowed age-class (the "masters") to bring their large body mass into play in initiating fights involving the most risky technique. The increasing risk of fighting when densities of grazing does are high in the fighting zone indicates the fallow deer males' ability to assess territory quality. Nonterritorial masters trying to intrude into another master's territory are ready to use the most risky fighting technique, whereas the territory holder tries to resolve the conflict by display alone. The structural similarities between fighting using the push technique and sparring indicate that the latter mimics the former, being a means by which the initiator of sparring might convey information about his own fighting ability and perhaps also obtain information about the fighting ability of his prospective opponents.

Individual Stability, Local Variability and the Cultural Transmission of Song in White-Crowned Sparrows (Zonotrichia Leucophrys Nuttalli)

The songs of 306 territorial male white-crowned sparrows were recorded between 1975 and 1983 in two study areas in San Francisco, California. Nestlings were banded and 47 sons whose father's songs had been recorded acquired territories. Some fathers had more than one son who acquired a territory. The songs of 263 territorial neighbours of the sons were also recorded. In addition, there were 32 females for whom both the father's and the mate's songs were available. The songs that were sung on the two study areas differed in a number of qualitative and quantitative aspects. For each area, there was change across years, in qualitative composition of song types, as well as considerable variability in the properties of the songs within dialect areas throughout the course of the study. There were 49 instances in which the song of a territory holder was recorded for more than one year. These individuals exhibited considerable stability of song across years. The song types of sons and fathers and of sons and neighbours were compared; Analysis of these songs indicated that some sons sang the song of the father, some adopted a song similar to that of the neighbours, and some had song with idiosyncratic elements that, in a few cases, remained in the population during succeeding generations. These data provided no support for the hypothesis that sons learned song preferentially from the father: there was no tendency for the quantitative characteristics of the songs of sons and fathers to be more similar than those of sons and neighbours, and when a father had two sons whose song was known, there was little tendency for the three songs to resemble one another. Finally, the songs of a father and his daughter's mate did not tend to resemble one another, indicating that females of this species do not choose as mates males that sing the same song as their father's. These results suggest that variability in transmission of song types may play a role in individual recognition, which in turn might aid a male to acquire a territory.

Male territoriality and mating success in Nannothemis bella (Uhler) (Odonata: Libellulidae)

Observations of territorial behaviour of male Nannothemis bella indicated that females only laid eggs on males' territories after copulating with the territory holder. Results of daily censuses of marked individuals on a study area suggested that a distinct subpopulation within the male population never retained a territory for more than 1 day on the study area. Such males tend to die or emigrate sooner than do males that hold a territory on the study area for more than 1 day at some time in their lives. Further observations of territorial behaviour showed that males holding territories for less than 1 day achieved copulations at significantly lower overall rates while on those territories than did males that retained territories for more than 1 day. We infer that all males attempt to hold territories for as long as possible, but under conditions of high population density a male must have a relatively high intrinsic "territory-holding ability" in order to hold a territory for more than 1 day. Census data indicated that males emerging late in the season were less likely to retain a territory for more than 1 day than males emerging earlier.

An Observer-Specific, Full-Season, Strip-Map Method for Censusing Songbird Communities

In this paper I describe and demonstrate a strip-map census method designed to provide a complete record of the composition and density of a temperate-zone breeding bird community through a period covering the peaks of breeding activity of all resident species and individuals. A route transecting the area of interest is laid out, flanked on each side by an unmarked strip of a width equal to the distance at which birds can be detected (the detection-threshold distance). All birds detected during uniform listening periods on frequent, closely scheduled, early morning traverses of the route are recorded with appropriate symbols at the moment of detection on simple line maps of the route. Because species differ in the distance at which their calls and songs can be heard and observers differ in their hearing acuity, each observer has an observer-specific strip width for each species. These strip widths are determined directly from the distribution of all detection points on the census maps at the end of the season. Multiplied by the length of the strip, they give the area of the strip for each species. The accumulations of detection-point clusters on summary maps for each species are interpreted as the territories of individual birds. Densities within the study area or segments of it are determined by dividing the number of equivalent territories (Σ wholes plus fractions) within the species-detection strip by the area of the strip. Song frequencies are determined for each individual territory holder by multiplying the proportion of listening periods during which the bird was heard by the proportion of that bird's territory that fell within the species' detectability strip. The method provides a continuous record, divisible into segments of any desired length, of the density, song activity, and distribution of individuals of each species through its breeding season. The detection-threshold distance and song-frequency values obtained can be used as species-specific conversion factors for translating simple detection counts to bird densities.

The savannah sparrow territorial system: can habitat features be related to breeding success?

We studied the biology of the savannah sparrow (Passerculus sandwichensis) in a tidal marsh – abandoned fields ecotone at Isle Verte, Québec, from 1976 to 1981 in an attempt to relate habitat features of the territories (size, vegetation structure and height, food abundance, and an index of foraging opportunities) with breeding success (success in attracting a mate and in fledging at least one young). The height of plant cover did not influence the selection of nesting areas by females. The index of foraging opportunities was highly variable and could not be related to the age of the territory holder (yearling or older), his mating status (breeder or bachelor), or to his breeding success (success in fledging at least one young). Territory size was not consistently influenced by these factors. We propose several reasons for the lack of relation between breeding performance and those features of habitat quality that we studied.

Territoriality and habitat selection of female snowy owls (Nyctea scandiaca) in winter

Territoriality of snowy owls (Nyctea scandiaca) was investigated near Calgary, Alberta, in the winters of 1976–1977 and 1977–1978. Males appeared to be nomadic, although some individuals remained in small areas for periods of up to 17 days. Many females defended territories of 150–450 ha for periods of up to 80 days. Territories of females contained some habitats in excess of their proportion on the study area. This represents selection of habitats with high prey availability. Owls spent more time in such habitats than in resource-poor habitats within their territories. Territory size was inversely related to the proportion of stubble field and the amount of "edge" habitat bordering stubble fields, on the territories. These findings are consistent with an earlier hypothesis that the size of feeding territories is regulated to provide the territory holder with a constant level of food. Juvenile females defended larger territories than did adult females, with higher proportions of nonpreferred habitats. We suggest that these differences result from the inexperience of juveniles in selecting and defending optimal winter territories.