The activity budget and use of territory by a tropical blenniid fish

Both sexes of Ophioblennius atlanticus (Valenciennes) maintain permanent territories, intermixed without pattern. They occur at a density of about 1.9 individuals per m² on shallow coral rock and comprise a significant portion of the benthic fish biomass. They are diurnal; about 60% of their time is spent resting, 15% swimming and 8.5% feeding. Feeding is concentrated in the afternoon and is time-minimized. Territory is used exponentially, about 50% of time being spent in about 15% of the territory. The relatively infrequent use of peripheral parts of a territory suggest that it is potentially compressible or expansible. This, in turn, leads to a conclusion that an optimum size can only be defined as a range and mat, normally, a territory includes more resources than the minimum for survival. Competition may be reduced between aegis corrivals of different species.     

Factors influencing detection of nesting crested caracaras

Management of crested caracaras (Caracara cheriway), focuses on nests identified during surveys. If no nests are found, management can be suspended. Thus, false negatives can have substantial consequences. We surveyed 49 breeding territories to assess factors with the potential to cause false negatives in detecting nests of crested caracaras and in observing adult birds. The probability that a nest would be detected on any given visit increased by about 0.5% for each hour of observer experience up to about 70 hours (our maximum). Experience did not affect the probability of observing an adult. The probability of detecting a caracara nest or observing an adult caracara decreased by 2.0–3.5% each hour after sunrise that a visit began. If visibility during any portion of a visit was obscured by fog or rain, the probability of detecting a nest decreased by as much as 60%, and the probability of observing an adult caracara decreased by about 50%. We provide a tool managers can use to calculate the likelihood of successful surveys. We recommend that managers disregard negative results from surveys conducted under conditions that are unlikely to yield positive results, and repeat those surveys under better conditions. © 2011 The Wildlife Society.     

Evaluating Habitat Quality for the Dusky Flycatcher

Abstract: We studied the dusky flycatcher (Empidonax oberholseri) at 8 sites in central Idaho, USA, in 2002 and 2003 to examine relationships among vegetation cover, density of breeding conspecifics, and indicators of habitat quality. Number of breeding territories and number of fledglings per hectare were positively associated, suggesting that the dusky flycatcher experienced increased reproductive success where it bred at the highest densities. However, the relationships between nesting success, annual reproductive success, number of fledglings per hectare, and amount of understory cover showed substantial annual variation. Nesting success did not differ significantly across sites or between years. Both reproductive success, expressed as young produced per hectare (range: 0.34–3.09 in 2002 and 0.79–3.82 in 2003) and young produced per nesting attempt (range: 0.71–2.78 in 2002 and 1.11–3.10 in 2003), differed across study sites in each year. Mean clutch size did not differ significantly among sites or years. Mean egg weight showed significant variation across some sites within years and was associated negatively with the 3 measures of reproductive success in 2002, although small sample sizes prevented reliable inference about the appropriateness of this measure as an indicator of habitat quality. Mean clutch size and mean egg weight were not associated with vegetation cover variables. Thus, dusky flycatcher reproductive success showed inconsistencies with individual vegetation measurements at the site scale. Forest managers who use vegetation treatments to increase amounts of understory shrub cover (e.g., by removing portions of the overstory conifer canopy) should increase densities of this species and, in turn, increase number of fledglings produced, but these responses appear to be better measured at the territory or nest scales than at the stand or site scales.     

Use of farmland by Ortolan Buntings (Emberiza hortulana) nesting on a burned forest area

Summary Most passerines have all-purpose territories in which both breeding and feeding take place. However, Ortolan Buntings (Emberiza hortulana) in Norway seem to depend on foraging areas outside nesting territories. We used radio transmitters to study patterns of farmland use by Ortolan Buntings nesting on a burned forest area. Territories on the forest burn were located closer to farmland than expected by chance. Males were absent from territories on average 27 % of the time and used foraging areas up to 2.7 km away from their territories. Males had to fly over an average of 1.4 territories of other males to reach those foraging areas. The distance between territory and closest area of farmland (range 40–460 m) did not affect the proportion of time absent from territories, or other measures of farmland use. However, there was a trend that duration of absences increased with territory-farmland distance among mated males, and duration of absences were shorter during the nestling period than before. Thus, it seems that minimizing travel costs may be a behavioural strategy. Even so, males with territories close to farmland were not more often paired than males further away from farmland. These findings indicate that the spatial distribution of one habitat (farmland) affects territory establishment and foraging behaviour of Ortolan Buntings nesting in another habitat (a forest burn).

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Nutzung von Ackerland durch Ortolane (Emberiza hortulana) einer benachbarten Brandfl?che

Zusammenfassung Bei den meisten Singv?geln ist das Revier sowohl Brut- als auch Nahrungsraum. Bei Ortolanen (Emberiza hortulana) in Norwegen, die auf Brandflachen brüten, scheint dies aber anders zu sein. Radiotelemetrische Untersuchen zeigten, dass sie von Nahrungsgründen au?erhalb der Brutterritorien abh?ngig sind. Die Nester auf den Brandflachen h?uften sich am Rand zum benachbarten Ackerland. M?nnchen waren durchschnittlich 27 % der Zeit vom Brutrevier abwesend und gingen his zu 2,7 km vom Brutplatz entfernt auf Nahrungssuche, wozu sie durchschnittlich 1,4 Reviere anderer M?nnchen überfliegen mussten. Der Abstand zwischen Brutrevier und n?chstem Nahrungsplatz (zwischen 40 und 460 m) hatte keinen Einfluss auf den Zeitanteil au?erhalb des Brutreviers. Die Dauer der Abwesenheit stieg jedoch bei verpaarten M?nnchen mit der Entfernung zwischen Brutrevier und Ackerland und sie war kürzer w?hrend der Nestlingsphase. Dies wird als Verhaltensstrategie zur Minimierung der Flugkosten interpretiert. M?nnchen mit Revieren n?her am Ackerland waren nicht h?ufiger verpaart als mehr entfernte Revierinhaber. Diese Untersuchungen zeigen, dass beim Ortolan die r?umliche Verteilung eines Habitats (hier Ackerland) einen Einfluss auf die Etablierung von Brutrevieren und das Nahrungssuchverhalten in einem anderen Lebensraum (hier Brandfl?chen) hat.