  Effective marine spatial plans require information on the distribution and
abundance of biological resources that are potentially vulnerable to
anthropogenic change. In North America, spatially-explicit abundance estimates
of marine birds are necessary to assess potential impacts from planned offshore
wind energy developments (OWED). Sea ducks are particularly relevant in this
context as populations of most North American species are below historic levels
and European studies suggest OWEDs. We modelled species occupancy using a
generalized additive model and conditional abundance with generalized additive
models for location, scale, and shape; the models were subsequently combined to
estimate unconditional abundance. We demonstrate this flexible, model-based
approach using sea ducks (Common Eider [Somateria mollissima], Black Scoter
[Melanitta americana], Surf Scoter [M. perspicillata], White-winged Scoter [M.
deglandi], and Long-tailed Duck [Clangula hyemalis]) in Nantucket Sound,
Massachusetts, USA, which supports some of the largest concentrations of
wintering sea ducks in eastern North America and where a 454-MW OWED is
proposed. Our approach to species distribution and abundance modelling offers
several useful features including (1) the ability to model all conditional
distribution parameters as a function of covariates, (2) integrated variable
reduction and selection among many covariates, (3) integrated model selection,
and (4) the efficient incorporation of smooth effects to capture spatiotemporal
trends poorly explained by other covariates. This modelling approach should
prove useful for marine spatial planners in siting OWEDs while considering key
habitats and areas potentially vulnerable to anthropogenic stressors. Moreover,
the approach is equally suitable for terrestrial or aquatic systems.
