‘O sibling, where art thou?’ – a review of avian sibling recognition with respect to the mammalian literature

Avian literature on sibling recognition is rare compared to that developed by mammalian researchers. We compare avian and mammalian research on sibling recognition to identify why avian work is rare, how approaches differ and what avian and mammalian researchers can learn from each other. Three factors: (1) biological differences between birds and mammals, (2) conceptual biases and (3) practical constraints, appear to influence our current understanding. Avian research focuses on colonial species because sibling recognition is considered adaptive where ‘mixing potential’ of dependent young is high; research on a wider range of species, breeding systems and ecological conditions is now needed. Studies of acoustic recognition cues dominate avian literature; other types of cues (e.g. visual, olfactory) deserve further attention. The effect of gender on avian sibling recognition has yet to be investigated; mammalian work shows that gender can have important influences. Most importantly, many researchers assume that birds recognise siblings through ‘direct familiarisation’ (commonly known as associative learning or familiarity); future experiments should also incorporate tests for ‘indirect familiarisation’ (commonly known as phenotype matching). If direct familiarisation proves crucial, avian research should investigate how periods of separation influence sibling discrimination. Mammalian researchers typically interpret sibling recognition in broad functional terms (nepotism, optimal outbreeding); some avian researchers more successfully identify specific and testable adaptive explanations, with greater relevance to natural contexts. We end by reporting exciting discoveries from recent studies of avian sibling recognition that inspire further interest in this topic

Chromosome number variation in two antipodean floras

Italy and New Zealand are very similar in shape, extension, altitudinal and latitudinal range but located in opposite hemispheres. This paper compares variation in chromosome number in these two hotspot regions. The results challenge previous ideas concerning links between geography and patterns of chromosome number variation

Threat-sensitive anti-predator defence in precocial wader, the northern lapwing Vanellus vanellus

Birds exhibit various forms of anti-predator behaviours to avoid reproductive failure, with mobbing—observation, approach and usually harassment of a predator—being one of the most commonly observed. Here, we investigate patterns of temporal variation in the mobbing response exhibited by a precocial species, the northern lapwing (Vanellus vanellus). We test whether brood age and self-reliance, or the perceived risk posed by various predators, affect mobbing response of lapwings. We quantified aggressive interactions between lapwings and their natural avian predators and used generalized additive models to test how timing and predator species identity are related to the mobbing response of lapwings. Lapwings diversified mobbing response within the breeding season and depending on predator species. Raven Corvus corax, hooded crow Corvus cornix and harriers evoked the strongest response, while common buzzard Buteo buteo, white stork Ciconia ciconia, black-headed gull Chroicocephalus ridibundus and rook Corvus frugilegus were less frequently attacked. Lapwings increased their mobbing response against raven, common buzzard, white stork and rook throughout the breeding season, while defence against hooded crow, harriers and black-headed gull did not exhibit clear temporal patterns. Mobbing behaviour of lapwings apparently constitutes a flexible anti-predator strategy. The anti-predator response depends on predator species, which may suggest that lapwings distinguish between predator types and match mobbing response to the perceived hazard at different stages of the breeding cycle. We conclude that a single species may exhibit various patterns of temporal variation in anti-predator defence, which may correspond with various hypotheses derived from parental investment theory

It Costs to Be Clean and Fit: Energetics of Comfort Behavior in Breeding-Fasting Penguins

), seabirds known to fast for up to one month during incubation shifts ashore.A time budget was estimated from focal and scan sampling field observations and the energy cost of comfort activities was calculated from the associated increase in heart rate (HR) during comfort episodes, using previously determined equations relating HR to energy expenditure. We show that incubating birds spent 22% of their daily time budget in comfort behavior (with no differences between day and night) mainly devoted to preening (73%) and head/body shaking (16%). During comfort behavior, energy expenditure averaged 1.24 times resting metabolic rate (RMR) and the corresponding energy cost (i.e., energy expended in excess to RMR) was 58 kJ/hr. Energy expenditure varied greatly among various types of comfort behavior, ranging from 1.03 (yawning) to 1.78 (stretching) times RMR. Comfort behavior contributed 8.8–9.3% to total daily energy expenditure and 69.4–73.5% to energy expended daily for activity. About half of this energy was expended caring for plumage.This study is the first to estimate the contribution of comfort behavior to overall energy budget in a free-living animal. It shows that although breeding on a tight energy budget, king penguins devote a substantial amount of time and energy to comfort behavior. Such findings underline the importance of comfort behavior for the fitness of colonial seabirds

A Longitudinal Study of Changes in Fluctuating Asymmetry with Age in Jamaican Youth

Fluctuating asymmetry (FA), random deviation from perfect bilateral symmetry, is an indicator of developmental stability. Examining the ontogeny of FA can illustrate whether symmetry is actively maintained as the organism grows or breaks down as perturbations accumulate with age. Previous studies of changes in human FA with age have been cross-sectional studies and give conflicting results. We analyzed data from a longitudinal study of bodily FA in Jamaicans, using a composite index of seven paired traits. In addition, 288 children (ages 5–12) were first measured in 1996, and many were re-measured in 2002 and 2006 (maximum age = 22 years). Both within-individual longitudinal comparisons and between-individual comparisons across age groups demonstrate changes in FA with age. In males and females, FA increased until around age 13, but the pattern of change differed between the sexes. In males, FA increased rapidly approaching adolescence and then slightly declined into early adulthood. The increase in female FA was more gradual and then leveled off. The patterns observed likely reflect accumulation of developmental errors over time, rapid physical changes during puberty (especially in boys), and then regulation of symmetry when transitioning into adulthood. Although most changes in symmetry over time probably reflect random processes, the magnitude and direction of asymmetry in an individual at one point in time tended to be positively (though weakly) related to asymmetry in later years, pointing to underlying differences among individuals in developmental stability