Silver-Haired Bats (Lasionycteris noctivagans) Found Ensnared on Burdock (Arctium minus)

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Burdock (Arctium spp.) is an invasive species from Eurasia, first reported in New England in 1638. It was common in Ontario by 1860, and is now considered an agricultural pest throughout its North American range (Royer and Dickinson 1999). Burdock's wide range can be attributed, in part, to the distinctive morphology of its seed casing, which has adhesive spines that readily attach to skin, fur, and feathers, enabling animal-based dispersal (Royer and Dickinson 1999). Burdock can pose a threat for small, flying vertebrates if the seed casing becomes entangled with the flight membrane of bats or the primary or secondary feathers of birds (for example, Lyon 1925; McNicholl 1988; Hager and others 2009). There are a number of published accounts of mortality for small birds found ensnared on Burdock including Ruby-throated Hummingbird (Archilochus colubris; McNicholl 1988; Nealen and Nealen 2000; Hinam and others 2004); Least Flycatcher (Empidonax minimus; Underwood and Underwood 2001; Hager and others 2009); Common Yellowthroat (Geothlypis trichas; Brown 1970); Blue-gray Gnatcatcher (Polioptila caerulea; Brewer 1994; McNicholl 1994); Ruby-crowned Kinglet (Regulus calendula; Van Damme 2005); and Golden-crowned Kinglet (Regulus satrapa; Dawe 1974), among others (for example, Burton 1994; Dean 1994; McNicholl 1994; Underwood and Underwood 2001). These accounts suggest that mortality due to Burdock may be relatively common for small birds (3.5-15.2 g; Van Damme 2005), especially since many similar events likely go unreported. Although mortality caused by Burdock has been most widely reported for small birds, Burdock may pose a similar threat for small bats. In 1892, approximately 12 bats, presumed to be Little Brown Bats (Myotis lucifugus) were found dead attached to Burdock in Illinois