Doctoral Thesis at Simon Fraser University (2019–present) The costs of parental care: Investigating the physiological and behavioral adaptations related to workload and costs of reproduction in two avian models, the European starling (Sturnus vulgaris) and zebra finch (Taeniopygia guttata).
How hard do free-living animals truly work? It has long been considered that some activities of free-living animals are energetically demanding or ‘hard work’, for example, avian migration. If animals are working hard, especially during reproduction, it is likely they might pay a ‘cost’ of increased workload. For example, a widely accepted view is that animals work sufficiently hard during breeding to incur ‘costs of reproduction’—that is, the idea that individuals are able to maximize lifetime reproductive success only by increasing workload to allocate resources to current offspring against the production of future offspring and self-maintenance. Nonetheless, over the past 50 years, studies of the trade-off between parental effort and survival have provided equivocal evidence, especially in female birds, with many failing to find any support while others find evidence against it. Therefore, if parental care is so costly, why is it so difficult to demonstrate negative (e.g., physiological) effects of the intense activity associated with chick-rearing?
The goal of my PhD thesis is to investigate several physiological and behavioral mechanisms wild-breeding birds may utilize to attenuate the costs of reproduction associated with increased workload and display degrees of individual variation in phenotypic plasticity during critical transitions in reproductive stages (i.e., incubation to chick-rearing).
Image 1. A photograph of a female zebra finch (Taeniopygia guttata) modeling a weighted backpack that I designed. The backpack is attached via a leg-loop harness.
Master's Thesis at Western Kentucky University (2017–2019) Published in Hormones & Behavior Effect of sleep loss on cognitive function and plasma corticosterone levels in an arctic-breeding songbird, the Lapland longspur (Calcarius lapponicus)
Sleep is a fundamental component of vertebrate life, although its exact functions remain unclear. Animals deprived of sleep typically show reduced neurobiological performance, health, and in some cases, survival. However, a number of vertebrate taxa exhibit adaptations that permit normal activities even when sleep is reduced. Lapland longspurs, arctic-breeding passerine birds that experience 24 h of sunlight on their breeding grounds in Northern Alaska, exhibit around-the-clock activity during their short breeding season, with an inactive period of ca. 4 h/day. Whether behavioral and physiological costs occur from sleep loss (SL) in this species is unknown.
Image 2. A male Lapland longspur (Calcarius lapponicus) in Barrow, Alaska.
To assess the effects of SL, wild-caught male longspurs were placed in captivity and trained to successfully learn two executive functions tasks; color association and spatial learning. For the color association task (Fig. 2a), a randomly chosen well in a six-well cell culture plate was covered with a blue chip and consistently baited with a mealworm larva while the randomly chosen well covered by the white chip remained unrewarded. For the spatial learning task (Fig. 2b), the well in the back-left corner was consistently baited with a mealworm. Successful completion of the color association and spatial learning task was marked by birds removing the blue chip and the back-left chip first before engaging with any other part of the task, respectively.
Birds were then placed in automated sleep fragmentation cages that utilize a moving wire to force movement every 1 min (60 arousals/h) during 12D (inactive period) or control conditions (during 12L; active period). After SL (or control) treatment, birds were presented with the color association and spatial memory tasks a final time to assess executive function. Baseline plasma corticosterone concentration, body mass, and satiety were also measured.
Figure 2. Cage designs used for the executive function tasks (cage tops removed). a, Color color association task. A six-well cell culture microplane was secured to the center of an acrylic insert (30.5 cm x 33.0 cm). b, Spatial learning task. Single wells were secured in each of the four corners of the cage on top of an acrylic insert.