Overlap in reproductive phenology increases the likelihood of cavity nest usurpation by invasive species in a tropical city

Multiple invasive cavity-nesting bird species can be present in a nest web, the network linking birds using cavities. We investigated the nest preferences and breeding phenologies of the cavity-nesting guild in the region surrounding Miami, Florida, USA, where invasive starlings, mynas, and parrots potentially usurp cavities from native woodpeckers and secondary cavity-nesters. We asked if the timing of reproduction determines which invasive species will usurp cavities from native birds with similar nest preferences. Nest usurpations between European Starlings (Sturnus vulgaris) and the woodpecker species present in Miami is well documented, but we predicted that a recently arrived sturnid species and introduced psittacids would also usurp nests. European Starlings had the largest breeding population of any species in our nest web, breeding during the peak of nesting season, and usurped the largest number of active nest cavities. We found that a small population of Common Mynas (Acridotheres tristis) usurped nests, sharing the peak-season nesting period with starlings and native woodpeckers. Parrots bred later than we expected, avoiding nest-site overlap with similarly large native birds that use cavities with similar characteristics. Parrots did not usurp any active nest cavities from native birds. Our results demonstrate how to use analysis of cavity characteristics and reproductive timing to evaluate threats to a cavity nest web posed by multiple invasive species. Common Myna currently usurp few nests; if they increase greatly in population, they could pose a problem for native cavity-nesters.

Notes from the Hastings Natural History Reservation

This chapter details the author's field notes from the Hastings Natural History Reservation. The author was particularly interested in studying acorn woodpeckers and their nest cavities. Acorn woodpeckers fascinate scientists because they live in groups, often with multiple breeding males and females, and nonbreeding helpers. The breeders share mates readily, and females lay eggs in a common nest, which is always a cavity nest. Moreover, they are quite vocal, even for woodpeckers; some would call them “articulate.” At Hastings, ornithologists annotate their field notes in “bird time” rather than “people time.” This is because birds do not transition to daylight saving time the way people do. The chapter then discusses the “ambush,” which is a capture technique developed at Hastings.

Adult emergence order in a community of cavity-nesting bees and wasps, and their parasites

Evaluating resource use and overlap through time and space among and within species having similar habitat requirements informs community-level conservation and coexistence, efforts to monitor species at-risk and biological invasions. Many species share common nesting requirements; one example are cavity-nest bees and wasps, which provision nests in dark and dry holes in wood, plant stems, or other plant-based materials that can be bundled together into ‘trap nests’. In this study, the adult emergence order of 47 species of solitary cavity-nesting bees and wasps, and their parasites (total N>8000 brood cells) were obtained from two hundred identical trap nests set up each year (over three years) to survey these populations across Toronto, Canada and the surrounding region. All brood cells collected were reared in a growth chamber under constant warming temperature and humidity to determine species identity, and adult emergence order. This order ranged from 0 to 38 days, with all mason bees (Osmia spp.) emerging within the first two days, and the invasive resin bee species, Megachile sculpturalis Smith significantly later than all others. Late emerging species i) exhibited significantly greater intraspecific variation in mean emergence day and ii) were significantly larger in body size, compared to early emerging species. Detailing natural history information at the species- and community-level, such as the adult emergence order of coexisting cavity-nesting bees and wasps and their parasites, can inform the timing of deployment of trap nests to support and monitor target species, and refine experimental design to study these easily-surveyed and essential insect communities.