Species rank of Isabela Oriole Oriolus isabellae and White-lored Oriole O. albiloris reinforced by song playback responses

Environmental BiologyConservation Biolog

Morphology, activity area, and movement patterns of the frugivorous monitor lizard Varanus Bitatawa

The newly described Varanus bitatawa is a large, frugivorous, monitor lizard endemic to the northern Sierra Madre mountain range in Luzon, Philippines. This study presents the first description of its ecology from tracking and camera trapping. We captured five adult lizards weighing 1.0-5.1 kg with snout-vent lengths (SVL) from 40-66 cm and total lengths from 100-164 cm. Activity areas were non-overlapping with a mean of 12,400 m(2); males (23,300 m(2)) had larger activity areas than females (5,200 m(2)). Capture and camera trap records indicate that lizards move most frequently between 1000 and 1500. Movements were characterized by straight line distances between trees with a mean distance travelled between trees of 79 m. Mean daily distance covered was 176 m with larger distances covered by males (228 m vs 142 m for females).Environmental BiologyConservation Biolog

A limit to sustained performance constrains trill length in birdsong

In birds, song performance determines the outcome of contests over crucial resources. We hypothesized that 1) sustained performance is limited within song, resulting in a performance decline towards the end and 2) the impact of song length is compromised if performance declines. To test these hypotheses, we analyzed the songs of 597 bird species (26 families) and conducted a playback experiment on blue tits (Cyanistes caeruleus). Our multi-species analysis showed that song performance declines after sustained singing, supporting our hypothesis. If the performance decline is determined by individual attributes (i.e., physical condition), our results explain how trill length can honestly signal quality. Our experiment showed that longer trills of high performance elicited a stronger response during territorial interactions. However, long trills that declined in performance elicited a weaker response than short, high-performance trills. A trade-off between the duration and performance quality of a motor display can be an important aspect in communication across taxa

Female blue tits sing frequently: a sex comparison of occurrence, context, and structure of song

Animal science

Diet and Habitat Requirements of the Philippine Endemic Frugivorous Monitor Lizard Varanus bitatawa

Little is known about the ecology and diet of Varanus bitatawa, a recently discovered monitor lizard endemic to the Sierra Madre Mountains of Northern Luzon. Here we present data that show that it has a seasonal omnivorous diet comparable to its southern congener Varanus olivaceus. Consumption of fruits from Pandanus sp., Canarium sp. and Microcos stylocarpa was evident in fecal samples, from spool and line tracking observations, and from camera trap images. The frugivorous diet was supplemented with snails and insects belonging to the orders Orthoptera, Phasmatodea and Coleoptera. Habitat of V. bitatawa was studied in lowland disturbed dipterocarp forest at an elevation below 300 m. In three sampled sites basal area of dipterocarp trees ranged from 16.23 to 84.14 m2 ha-1, total tree density from 624.6 to 1021.4 trees per ha-1 and density of Pandanus from 115.15 to 222.30 trees per ha-1. Predominantly arboreal, V. bitatawa showed reliance on large sentinel trees. Of trees utilized, 47.4% were estimated at over 30 m tall with a mean circumference at breast height (CBH) of 176.28 cm and were significantly larger than the mean CBH of trees in sampled habitats. Shy and reclusive, V. bitatawa is likely to be vulnerable to disturbance. Illegal selective logging further degrades remaining habitat threatening the large dipterocarp trees on which they rely. Continued and improved protection of the forests within the Sierra Madre Mountain Range is imperative to safeguard the future of this restricted range species.Conservation BiologyEnvironmental Biolog