(1) Ecological partitioning of resource use among canopy burying beetles – Nicrophorus pustulatus is the only local burying beetle species that is more common in the forest canopy than on the ground. This species appears to use resources associated vertebrate reproduction for breeding, including snake eggs, dead bird nestlings, and discarded carrion at raptor nests. Other species of burying beetle, however, also sometimes occur in the canopy, leading the question: why don't other species of Nicrophorus also use resources associated with vertebrate reproduction, just like pustulatus? This project would involve experiments in nature using nest boxes with mice carcasses, testing the importance of height above the ground versus substrate in determining which burying beetle species breed on carrion. 

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(2) Do behaviourally subordinate species have greater ecological breadth? — In 1974, Douglas Morse (American Naturalist) described a repeated pattern of socially dominant and subordinate species segregating along environmental gradients. When the dominant species was removed, the subordinate expanded its distribution, suggesting that subordinate species had greater ecological breadth – they were adapted to their own distribution and resources, and to those of the dominant species as well. To date, only one study has independently tested this hypothesis (Freshwater et al. 2014, Ecology) and, surprisingly, found no difference between the ecological breadths of closely related dominant and subordinate species of birds (examining diet, foraging behaviour, nest sites, and habitat). This test, however, examined ecological breadth in locations where dominant and subordinate species co-occurred, and thus dominant species could have restricted the use of resources and habitats of the subordinate species. This proposed project would extend the work of Freshwater et al. (2014) to examine the ecological breadth of closely related dominant and subordinate species in areas of sympatry and allopatry, allowing a direct comparison of ecological breadth in areas with and without dominant species. The work would provide one of the few direct tests of Morse's hypothesis, and will further our understanding of how important ecological traits covary with the position of species within a social dominance hierarchy.

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(3) What ecological traits covary with behavioural dominance of species? — Previous work in our lab (Freshwater et al. 2014, Ecology) was the first to describe repeated patterns of trait divergence that depended upon the position of a species within a social dominance hierarchy. Specifically, subordinate species of birds arrived earlier on their breeding sites, initiated breeding earlier, had lower annual adult survivorship, laid larger eggs for their weight, and migrated greater distances, than closely related, dominant species. These patterns were exciting because they suggested that important traits related to phenology, life history, and migration are influenced by where a species sits within a social hierarchy of other species. The work was based on an analysis of 65 closely related species pairs of North American birds – all of the data on dominance interactions among congeners that was available at the time. Today, we have dominance data for ~200 species pairs of birds from around the world. Are the patterns of trait divergence evident in North American dominance hierarchies representative of birds from around the world? Are other patterns of trait divergence (e.g., geographic range size, distribution) evident among dominant and subordinate species when addressed with a larger sample? This project would revisit some of the questions addressed by Freshwater et al. (2014) using a larger, more powerful, global dataset on dominance relationships among birds.

 

(4) The influence of body size and pairing status on carcass burial speed and depth – Carcass burial by burying beetles is believed to be an adaptation to reduce competition, with quick and deep burial reducing the likelihood of losing a carcass to other scavengers (including conspecifics, congeners, other invertebrates, and vertebrates). Evidence suggests that larger size and cooperation may help speed burial and increase burial depth, but experimental tests in nature are lacking. This study would test these ideas using a semi-natural experimental setup using Nicrophorus orbicollis.

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(5) Are dead squirrels the disco for Nicrophorus burying beetles? – Burying beetles rarely use vertebrate carcasses heavier than 200g for breeding and most of our local species use carcasses much small than this. Gray Squirrel carcasses weigh 400-600g - much too large for Nicrophorus to use for reproduction - and yet Nicrophorus sayi (and possibly N. orbicollis) have been observed to congregate on squirrel carcasses, form pairs, and mate, particularly in areas of the carcass with little fur. This project would test among the hypotheses that Nicrophorus burying beetles (H1) are able to breed on dead Gray Squirrels, (H2) use dead Gray Squirrels as a site to feed, court and mate, or (H3) use dead Gray Squirrels only as a food source for adults; they do not usually breed, court, or mate on them. Given that other non-Nicrophorus carrion beetles (Sylphids) commonly breed on large carcasses, including squirrels, this project would provide important insights into resource partitioning among beetles.

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(6) Carcass size as a resource gradient promoting ecological partitioning in Nicrophorus beetles – Nicrophorus defodiens at our field site is a bit of an enigma. They occur in small numbers, don't seem to use distinct habitats or seasons, and are evicted from vertebrate carcasses by the larger Nicrophorus every time they try to breed. How does defodiens persist? One idea based on previous work elsewhere is that defodiens can use small carcasses for breeding that other species can't use, allowing them to persist on a unique resource despite the larger competitors. This project will test this hypothesis by placing mice carcasses of different sizes in nature and recording which species of burying beetle breed on different-sized mice. 

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7. Behavioural dominance interactions among hummingbird species – Aggressive interactions among species typically have a consistent outcome: one species usually wins, and the other usually loses. But on occasion, these consistent patterns among species break down, such as where interactions occur between individuals of different sexes, ages, and conditions. The likelihood and outcome of aggressive interactions can also be influenced by the resource and feeding state of the individual. For example, individuals who have just fed or have lots of food available may be more likely to give way to another individual rather than engage in a fight. The goals of this project are to (i) document aggressive interactions among hummingbird species at a feeder in Peru and/or Ecuador, (ii) test the idea that outcomes to these interactions sometimes vary, and (iii) test if resource availability, feeding status, or moult (changing of feathers) influences the likelihood of variation in aggressive outcomes. The work will rely on live stream video of hummingbird feeders (sorry, no field work to South America!), and will provide quantitative measures of dominance interactions among some poorly known Andean hummingbird species.

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