Piping Plover - U.S. Fish and Wildlife Service

fidelity of Atlantic birds, potentially as a consequence of reduced spatiotemporal variability
in habitat conditions. Conversely, greater temporal climatic variation may cause flooding or
complete desiccation of habitats used by interior populations, thereby forcing more dispersal.
This difference in genetic structure between C. m. melodus and circumcinctus may reflect
important adaptations to differences in habitat stability, although we cannot exclude the
possibility of a plastic (i.e., not hereditary) response to varying environments. Furthermore,
while C. m. circumcinctus breed on a range of habitat types (see discussion in section
2.1.3.1), habitat factors such as coastal tides, which affect C. m. melodus (but not C. m.
circumcinctus) nest site selection and foraging behaviors during critical stages in the
breeding cycle, may constitute an important ecological difference between subspecies.
Casual comparison of studies suggests other possible behavioral differences (e.g., prevalence
and timing of brood desertion by female parents, rates of inter-year mate retention) between
subspecies, but no formal analyses have been conducted.
In 2001, the Canadian Committee on the Status of Endangered Wildlife in Canada
recognized C. m. melodus and C. m. circumcinctus as separate taxa and designated each
subspecies as “Endangered” (Department of Justice Canada 2002). This superseded 1978
and 1985 designations assigned to the entire Canadian population of piping plovers
(COSEWIC 2001).
We are not aware of any current publications in the peer-reviewed literature that reject these
subspecies. S. M. Haig, first author of a 1988 allozyme study (Haig and Oring 1988a) that
failed to detect differences supporting piping plover subspecies, is also a co-author of Miller
et al. (2009). Thus, this more recent study employing modern and variable genetic
information systems to analyze a substantially larger data set fully supersedes Haig and
Oring (1988a).
The subspecies C. m. melodus exactly coincides with the geographic coverage of the Atlantic
Coast piping plover recovery plan (USFWS 1996), while the Great Lakes plan (USFWS
2003) and the Northern Great Plains plan (USFWS 1988b) pertain to C. m. circumcinctus.
2.1.3 Application of the 1996 DPS policy
Section 3 of the ESA defines “species” to include subspecies and “any distinct population
segment of any species of vertebrate fish or wildlife which interbreeds when mature
(emphasis added).” In 1996, the USFWS and the National Marine Fisheries Service
published a joint policy guiding the recognition of DPSs of vertebrate species (61 FR 4722).
As discussed in section 2.1.2 above, new information supports subspecies designation for C.
m. melodus and circumcinctus. However, because the piping plover is a vertebrate listed
prior to 1996, we evaluate evidence for DPSs within these two subspecies (see 61 FR 4724:
“The Services maintain that the authority to address DPSs extends to species in which
subspecies are recognized …”).
The DPS policy specifies three elements to assess whether a population segment under
consideration for listing may be recognized as a DPS: (1) the population segment’s
discreteness from the remainder of the species to which it belongs, (2) the significance of the
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