Bird courtship displays are frequently multi-modal displays that may provide diferent information about the signaler’s qualities for female choice. We became interested in this species since grassquits are unusual in that males display from specific locations at very high rates from perches that are close to other displaying males, which allowed us to quantify display traits under natural conditions while following multiple birds in the same breeding area. The males of this tropical granivorous species display repeatedly and usually nest in in dense goupings with small terrritories and the species was originally labelled as a lekking species; the only oscine breeder in the New World that lekked. We now know the females nest on the male’s territory and the male builds the nest and helps feed the chicks. Features that are not usuallly found in lekking species.The courtship displays are multimodal integrating motor and acoustic elements in addition to the differences in the very conspicuous male breeding plumage. Some males call while frequently leaping from a perch and making the call. Others coutall without leaping. We looked at the various components of the courtship display to see whether some of the signals were more important than others in female choice and if so which ones. We also looked to see whether all females were responding to the same signals since we also found that extra-pair paternity was exceptionally common and ranged from 8-34% of all nestlings and 11-47% of all broods. We examined the displays and the reproductive success to see what signals the social mate responded to, and whether the extra-pair females responded to the same signals as the pair females. [more]

To estimate the past and future impact of urbanisation on birds, it is important to understand the mechanistic underpinnings of a physiological response to anthropogenic stress. It is well known that urban pollution increases oxidative stress - a state when the antioxidant system is overwhelmed by oxidants, which may cause tissue damage linked to disease and senescence. Urban great tits (Parus major) have, repeatedly, shown to have a higher antioxidant activity than rural conspecifics, sometimes sufficient enough to prevent tissue damage and sometimes not. Regardless, an increased antioxidant defence is probably not cost free for urban birds, which is why we need to understand the underlying mechanisms. Is it a result of: i) the evolutionary history (i.e. a strong selection pressure for greater antioxidant capacities in urban habitats); ii) the present environment (i.e. direct physiological up-regulation in response to current urban stressors); or iii) the individual history combined with the present environment (i.e. developmental programming of gene regulation and the potential for match/mis-match between environment and optimal physiological response). By using the European great tit as our model system, my group address these three mechanistic pathways for generating variation in antioxidant capacities between populations and individuals. [more]

In eight groups of animals, including humans and songbirds, juveniles are understood to learn vocalizations by listening to adults. Experimental studies of laboratory-reared animals support this hypothesis but we lack experimental evidence of vocal learning in wild animals. I developed an innovative playback technology involving automated loudspeakers that broadcast songs with distinctive acoustic signatures. My collaborators and I used this technology to simulate vocal tutors in the wild and conducted year-long tutoring sessions to five cohorts of free-living migratory Savannah Sparrows. We confirm that wild birds learn songs by listening to adult conspecific animals, and we show that they pass these songs on to subsequent generations. Further, we provide the first experimental evidence in the wild that the timing of exposure to tutor song influences vocal learning: wild Savannah Sparrows preferentially learn songs heard during both their natal summer and at the outset of their first breeding season. This research provides direct experimental evidence of song learning by wild animals and shows that wild birds learn songs during two critical stages of development early in life. [more]

Human activities are globally pervasive. Although applied ecology and conservation biology has typically focused on how changes in vegetation or land cover influence wild populations and communities, growing evidence suggests that changes in other ecological dimensions, such as the acoustic and lit environment, can have comparable or larger ecological consequences than land cover changes. In this talk, I will discuss my lab’s use of natural and manipulative field experiments, plus large-scale databases, to understand how changes to the acoustic environment and light regimes can influence behavior, reproduction, distributions and ecological interactions. I will focus primarily on birds, but highlight key examples of how changes in sensory environments are highly relevant to human health and wellbeing. [more]