Structural support, not insulation, is the primary driver for avian cup-shaped nest design

The nest micro-environment is a widely studied area of avian biology, however, the contribution of nest conductance (the inverse of insulation) to the energetics of the incubating adult and offspring has largely been overlooked. Surface-specific thermal conductance (W °C−1 cm−2) has been related to nest dimensions, wall porosity, height above-ground and altitude, but the most relevant measure is total conductance (G, W °C−1). This study is the first to analyse conductance allometrically with adult body mass (M, g), according to the form G = aMb. We propose three alternative hypotheses to explain the scaling of conductance. The exponent may emerge from: heat loss scaling (M0.48) in which G scales with the same exponent as thermal conductance of the adult bird, isometric scaling (M0.33) in which nest shape is held constant as parent mass increases, and structural scaling (M0.25) in which nests are designed to support a given adult mass. Data from 213 cup-shaped nests, from 36 Australian species weighing 8–360 g, show conductance is proportional to M0.25. This allometric exponent is significantly different from those expected for heat loss and isometric scaling and confirms the hypothesis that structural support for the eggs and incubating parent is the primary factor driving nest design.Caragh B. Heenan and Roger S. Seymou

Biology of Invasive Monk Parakeets in South Florida

Monk Parakeets (Myiopsitta monachus) have been in Florida for \u3e40 yrs, having been imported by the thousands for the pet trade. This conspicuous, charismatic species is now widely established, but relatively little is known about its population biology outside South America. We examined 845 parakeets from 385 nests from nest removals and collections by utility company personnel in 2003/2004 and 2006/2007 to document body size and aspects of reproductive biology and primary molt. Body measurements confirm Monk Parakeets in south Florida belong to the monachus subspecies. Adult males averaged 1.5 to 3.5% larger than females, but the body mass of females exceeded that of males during March–May, the period of egg development. The breeding season in south Florida commences in late winter/early spring with fledglings first appearing in the second week of June. Nest contents (eggs plus nestlings) averaged 5.6 for multiple-entry nests compared to 4.9 for single-entry nests. Over 94% of the adults we examined were replacing primary feathers during June–August. The extent and timing of breeding and molt in south Florida are virtually identical to those in South America, although offset by ~6 months. Monk Parakeets in south Florida retain a fixed annual cycle characteristic of the ancestral population, but their flexible behavior enables them to adapt and thrive in new environments