Social experience can modify the behavior of adult animals, and this type of behavioral plasticity associated with territorial aggression has been observed in several species including green anole lizards. Previously dominant animals were more aggressive to a novel stimulus in a new context than previously subordinate animals after 10 days of agonistic interaction. This behavioral shift could be beneficial to an animal by increasing survival and/or reproductive success to maximize its fitness. Behavioral modification through social experience can involve alteration in some physiological properties such as variations in hormone titer and hormone receptors. Steroid hormones such as testosterone (T) and corticosterone (Cort) and neurotrasmitters such as arginine vasotocin (AVT) are well known for their association with territorial aggression. Hormonal mechanisms underlying the control of this behavior are, however, context dependent, temporally dynamic, and evolutionarily very diverse. I performed experiments aimed at gaining insights into the proximate mechanisms underlying status-dependent behavioral differences in territorial aggression. First, steroid binding globulins of green anole lizards were analyzed and the presence of androgen-glucocorticoid binding globulins and sex-hormone binding globulins (SHBG) was established. Next, status differences in steroid hormone levels and the temporal pattern of hormone changes were assessed. We found that winners/dominants had elevated total T levels shortly after the onset of fighting and reduced SHBG after 10 days of agonistic interaction. These changes seemed to cause sustained increases in free T levels in winners/dominants throughout 10 days of agonistic interactions. Then, androgen receptor (AR) mRNA density levels were compared in dominant and subordinate animals. The result showed that the preoptic area (POA) and anterior hypothalamus AR mRNA density levels were higher in dominants than subordinates shortly after the agonistic interaction. Lastly, AVT immunoreactive cell counts were compared in dominant and subordinate animals. We found that subordinate animals had reduced AVT immunoreactive cell counts in the POA compared to that of dominants or control males. Findings from this dissertation suggest possible mechanisms that might be responsible for status dependent behavioral differences in territorial aggression: elevation in T and reduction in SHBG capacity, and sustained elevation of AVT immunoreactive cell counts in the POA. / text

This thesis investigated the use of song repertoires during territorial defense of the song sparrow, Melospiza melodia. The functional and adaptive significances of repertoires in the order Passeriformes were reviewed. Within the family Fringillidae, an examination of repertoire size and life history features of different species revealed no significant correlations. / Observations of six neighboring song sparrows yielded information about the relative uses of repertoire-dependent and repertoire-independent mechanisms in coordinated song interactions, as well as in signalling agonistic probabilities. The behavior of song switching, independent of the identities of song types, was found to most effectively perform both types of functions. / A series of playback experiments tested and supported the hypothesis that the song sparrow's rate of switching song types increases with agonistic stimulation. Song versatility, rather than switching rate per se, was found to be an appropriate agonistic stimulus.

The variable plumage characteristics of the sub-adult male cohort of the red-winged blackbird (Agelaius phoeniceus) are described. At one extreme of the plumage variation, there are a group of sub-adult males that are indistinguishable from the adult males. These birds can only be correctly aged by cloacal examination for the bursa of Fabricius in the autumn. At the other extreme, approximately 4% of the population are near perfect female-mimics. A simple scoring system based on the interspersion of dark feathers in the epaulet is presented, which permits classification of the sub-adult males into 1 of 6 plumage classes. These epaulet classes are significantly correlated with other traits of the plumage. / Age when entering the prebasic molt, and the physical condition of the sub-adult male may influence the development of the varied plumage characteristics. / The distribution of the plumage characteristics of a population of sub-adult males collected at a major blackbird roost in the province of Quebec is described for birds captured in the fall and spring. The spring plumage characteristics are more variable than the fall, a phenomenon which is not consistent with plumage wear as has been previously reported, but which may be related to a prealternate molt which the birds undergo. The prealternate molt is prevalent in some but not all of the contour feather tracts, and is restricted to females and the sub-adult male cohorts. / An age- and sex-specific spring migration of red-winged blackbirds is examined. Adult males arrive to the spring roosts first, followed by yearling males and then females. A similar pattern of dispersal to the breeding territories is described. Within the subadult male cohort, the birds with the most adult-male like plumage traits arrive at the vernal roosts first. / The characteristics of the prealternate molt and differential spring migration are discussed in relation to the pressures of sexual selection on the respective age and sex cohorts. / The adaptive significance of variable sub-adult male plumages and delayed plumage maturation in passerines is evaluated. Several competing hypotheses have been advanced to describe the phenomenon of delayed plumage maturation. These hypotheses are reviewed, and a test is proposed which unequivocally differentiates between the various alternatives. (Abstract shortened with permission of author.)

Thesis (PH.D.)--Michigan State University. Zoology Ecology, Evolutionay Biology, and Behavior, 2008. / Title from PDF t.p. (viewed on Aug. 11, 2009) Includes bibliographical references (p. 64-72). Also issued in print.

The population biology and socio-spatial organisation of the woodland dormouse, Graphiurus murinus (Desmarest, 1822), was investigated in a riverine forest at the Great Fish River Reserve (GFRR), South Africa. Data were collected by means of a monthly live trapping and nestbox monitoring programme. Between February 2006 and June 2007, 75 woodland dormice were trapped and/or found in nestboxes and marked: these were 39 adults (13 males, 21 females, five undetermined) and 36 juveniles (five males, 14 females, 17 undetermined). The population showed a steady increase from June 2006–November 2006 and a peak in December 2006–January 2007 as a result of the influx of juveniles. The minimum number of dormice known to be alive (MNA) varied between 40 in December 2006– January 2007 (summer), and a low of three in June 2007 (winter). The range in population density was therefore between 1.2 and 16 dormice per ha. Winter mortality and/or spring dispersal accounted for the disappearance of 55 percent of juveniles. The overall annual adult:juvenile ratio was 1.08. The overall sex ratio was 1.94 female per one male. In females, reproductive activity was observed from September 2006 to end January 2007. The pattern observed in males was similar, as dormice with descended testes were exclusively found from October to end January. Females gave birth during the second half of October to beginning of February. Litters (n = 11) consisted of an average (± SD) 3.73 ± 0.47 young. Over the study period, 27 dormice were trapped or found in nestboxes more than eight times, thus allowing me to estimate their home range size and the spatial overlap between these individuals. On average, dormouse home range size was 2,514 m2 (range: 319 – 4,863 m2). No difference was recorded between one-year old adults and older adults, or between all adults and juveniles. However, adult male dormice (3,989 m2, n = 5) had home ranges almost twice as large as females (2,091 m2, n = 9). No similar trend was found in juveniles. Intrasexual home range overlap was on average 62 percent in adult males, and 26 percent in adult females. However, females overlapped with more neighbouring female home ranges than did males with neighbouring male home ranges, so that, as for males, only small parts of female home ranges were really exclusive. On average, males overlapped a larger Abstract Ecology of woodland dormice M.Sc. Thesis 16 proportion (48 percent) of female home ranges than did females with neighbouring male home ranges (27 percent). In addition, males overlapped with significantly more female home ranges (7.8) than did females with male home ranges (4.9). Trapping success and nestbox data agree with the socio-ecological model. Females showed increased mobility during summer, more likely to find suitable nesting sites, and food for milk production during the reproductive season. The use of nestboxes, however, was constant throughout the year. In males, both the trapping success and nestbox use were higher during the mating season (spring), when an increased mobility and occupation of nestboxes probably increased the chances to locate and mate with (a) receptive female(s). Hence, food and (artificial) nest sites may constitute an important resource for females, whereas females seem to represent the main resource for males. Although food availability was not determined, a comparison of female and male distribution patterns provided interesting information on the mating system of woodland dormice. In GFRR, the dispersion pattern of female woodland dormice was “rather” clumped, i.e. females were non-territorial. As some females showed a dyadic intrasexual overlap of up to 90 percent, and population density was very high at the study site, this may indicate that food was very abundant and/or renewed rapidly. Based on the wide range of birth dates observed during the study period, females clearly come into oestrus at different times. In such circumstances (asynchronous sexual receptivity in females), the Female in Space and Time Hypothesis (Ims 1987a) predicts that males will be non-territorial and promiscuous. Live-trapping, nestbox use and home range data indeed suggested that male woodland dormice do not defend territories, but search for and aggregate around receptive females during the mating season.

No description available.

No description available.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Please refer to fulltext for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming

Ecological divergence between Blackcaps and Garden Warblers appears to be incomplete. They resemble each other closely in morphology and their foraging behaviour and food (in the breeding season) are at least broadly similar. Nevertheless, they are sympatric and occur together in a wide range of habitats although Garden Warblers are proportionately commoner in lower, denser vegetation. The two species are strongly interspecifically territorial where they occur together. However, Blackcaps are more interspecifically aggressive than Garden Warblers and are clearly dominant to them in interactions. Blackcaps respond just as strongly to playback of Garden Warbler song as they do to that of Blackcap song. They sometimes intrude into Garden Warbler territories and seek- out and chase the territory holders. In contrast, with rare exceptions, any Garden Warblers which intrude into Blackcap territories are attacked and chased until they leave the area. Also, during song playback experiments, Garden Warblers approach the loudspeaker less closely in response to Blackcap song than they do to Garden Warbler song. Many Blackcaps arrive on the breeding grounds before the earliest Garden Warblers do. A removal experiment, in which such established Blackcaps were systematically removed, showed that some of them had been keeping-out potential Garden Warbler settlers, since the latter then readily established territories and bred in a large part of the Blackcap-free zone. Normally, Garden Warblers have their territories outside Blackcat>-occupied habitat, partly because they are prevented by the aggressiveness of the Blackcaps from settling elsewhere. However, observation and song playback experiments have shown that, once established, Garden Warblers do defend their territories against both conspecifics and Blackcaps. Blackcaps have recently increased dramatically in Britain and Garden Warblers have decreased simultaneously. However, although Blackcaps can limit the local breeding densities of Garden Warblers in any one year, it is not yet clear whether Blackcap numbers are a significant factor in determining the total sizes of Garden Warbler populations.

No description available.