1,721,098 research outputs found
Stima di distribuzione ed abbondanza del piccione domestico Columba livia var. domestica nell’area urbana del Comune di Piacenza
No full textLe popolazioni di piccione domestico Columba livia var. domestica hanno mostrato un notevole incremento
numerico negli ultimi anni, generando numerosi problemi in ambiente urbano ed extraurbano (Johnston & Janiga
1995). Poter comprendere la distribuzione della specie in relazione alle variabili ambientali è essenziale al fine di
poter sviluppare piani di controllo idonei. In tale contesto, in collaborazione con il Comune di Piacenza, è stato
avviato un piano di monitoraggio della popolazione, volto a migliorare la gestione della specie, tramite il metodo
del distance sampling (Giunchi et al. 2007). L’area urbana comunale è stata suddivisa in due zone (centro e
periferia), omogenee sia architettonicamente che dal punto di vista di idoneità ambientale per il piccione
domestico. All’interno delle due aree sono stati posti in modo random 60 transetti di ca. 300 m, percorsi due volte
l’anno (febbraio e novembre) nelle prime due ore dopo l’alba, al fine di riuscire a contattare tutti gli individui
presenti lungo essi. I dati raccolti, successivamente georeferenziati, sono stati elaborati tramite software per
produrre una funzione di contattabilità per ciascuna zona che, mettendo in relazione gli individui osservati con la
distanza perpendicolare di essi dal transetto, ha permesso di ottenere una prima stima generale della popolazione.
Le funzioni di contattabilità sono state utilizzate per generare modelli di abbondanza della popolazione tramite la
tecnica del Density Surface Modelling (DSM, Miller et al. 2014). Il DSM permette di mettere in relazione le curve
di contattabilità con le variabili ambientali considerate all’interno delle due zone. Vengono discussi i risultati
ottenuti da entrambe le metodiche e le differenze riscontrate tra essi
Head ornaments in owls: what are their functions?
No full textWe studied head ornamentation in owls by focussing on the hypothesis that it may serve both intra- and interspecific communication. We carried out pairwise comparisons of morphological, ecological and behavioural traits on a subset of closely related species with contrasting head ornamentation patterns. We found that the degree of head ornamentation was associated with habitat and activity rhythm, highly ornamented species (e.g., most of the genus Bubo) living preferentially in open habitats and being active by day, but not with body size. Although our results do not exclude the possibility that head ornaments may represent a warning mechanism to startle predators and mobbers, they nevertheless suggest that such signals have evolved for visual communication with conspecifics, being more expressed in species that may use them more effectively without incurring the risk of predation or disturbance
Does bib size act as a status badge in territorial Reed Buntings (Emberiza schoeniclus)?
No full textField experiments on the value of plumage as status badge
Delayed reproduction among Great Bitterns Botaurus stellaris breeding in ricefields
Full text linkGreat Bitterns bred successfully in ricefields in northern Italy, despite a marked delay to the breeding season compared to natural wetlands in the same geographical area. Great Bitterns show a phenotypic plastic response to environmental change and to variation in peak resource availability. The breeding season of bitterns nesting in Italian ricefields is delayed compared to those breeding in natural wetlands. Our data suggest that Great Bitterns can successfully reproduce in ricefields. The delayed breeding season of birds nesting in ricefields compared to those nesting in natural wetlands of the same geographical area did not seem to affect the reproductive parameters. Indeed, breeding in ricefields occurs at a time when this habitat offers both abundant feeding resources
Sperm removal and ejaculate size correlate with chelae asymmetry in a freshwater crayfish species
Full text linkAsymmetry in traits of sexual relevance may
impair copulation behaviour and sexual performance of
males, ultimately resulting in a fitness cost. Freshwater
crayfish males use chelae, a sexually selected trait, to secure
and position the female prior to and during mating. Thus, a
relatively large chelae asymmetry, resulting from accidental
loss and regeneration of one cheliped after autotomy, could
have great consequences for male sexual behaviour. We
studied copulatory behaviour and sperm expenditure of
males paired to a mated female in Austropotamobius
italicus, a freshwater crayfish species where both male
and female mate multiply and where last-mating males are
able to actively remove previously deposited sperm. We
aimed at assessing whether male sperm removal and
expenditure varied according to sperm allocated by firstmating
males, and according to copulation behaviour and
phenotypic traits (carapace length, chelae length and relative
chelae asymmetry) of second-mating males. Secondmating
males did not adjust their ejaculate size in relation to
first-mating male ejaculate, nor to the first-mating male’s
sperm removed. Moreover, the amount of sperm removed
by second-mating males increased with increasing firstmating
males ejaculate size, and first-mating male sperm
remaining after removal did not correlate with the original
first-mating male ejaculate size. Interestingly, the amount of
sperm removed by second-mating males decreased with
increasing relative chelae asymmetry, while increasing
with male body size. However, second-mating (but not
first-mating) asymmetric-clawed males produced larger
ejaculates than symmetric-clawed ones. Importantly, the
proportion of second-mating male sperm remaining after
the two matings did not vary with relative chelae asymmetry
nor with body size of second-mating males. Thus, small,
asymmetric-clawed crayfish males appear to adopt sperm
allocation tactics that allow them to fully compensate for
their inferior sperm removal ability
Long-term trends of heron and egret populations in Italy, and the effects of climate, human-induced mortality, and habitat on population dynamics
No full textNonrandom mating, mate choice, and male-male competition in the crayfish Austropotamobius italicus, a threatened species
No full textUnder the rationale that behavioral studies may contribute to the conservation of threatened species, we analyzed mating behavior of the crayfish Austropotamobius italicus in the laboratory. Our objectives were to investigate whether nonrandom mating by size occurs in this species and to explore the role exerted by mate choice and male-male competition in inducing mating. We observed 17 "quartets" (one female and three differently sized males), divided into three groups based on the female size. To understand the influence of male-male competition on mating, we compared six quartets with six "duets" (one female and one male). Our results clearly show that mating in A. italicus is nonrandom caused by the clear mating advantage of larger males. In fact, as compared to smaller size categories, large males paired more often and for a longer time, and interrupted the final phase of mating less frequently. Male size-advantage mostly derives from an active female choice for large partners, combined with dominance of big males in intrasexual competition. However, a restricted mating period and the low number of receptive females may make males relatively indiscriminate in their overt behavior towards females. Female selection of big males and male-male competition over mates, also in the form of sperm competition, should result in a skewed reproductive success among males. As a consequence, populations with few big males would be characterized by a low heterozigosity and therefore by little genetic variation upon which selection acts. Our results should warn managers to pay more attention to the size structure of crayfish populations that are used for reintroductions
Recent declines in urban Italian Sparrow Passer (domesticus) italiae populations in Northern Italy
No full text
Plumage redness of Scops Owls increased with temperature and rainfall during the last century
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