Habitat Patch Occupancy Dynamics of Glaucous‐winged Gulls (Larus Glaucescens) Ii: A Continuous‐time Model

Abstract

ABSTRACT. The diurnal distribution and abundance dynamics of loafing Glaucous‐winged Gulls (Larus glaucescens) were examined at Protection Island National Wildlife Refuge, Strait of Juan de Fuca, Washington. Asynchronous movement of gulls among three habitat patches dedicated to loafing was modeled as a function of environmental variables using differential equations. Multiple time scale analysis led to the derivation of algebraic models for habitat patch occupancy dynamics. The models were parameterized with hourly census data collected from each habitat patch, and the resulting model predictions were compared with observed census data. A four‐compartment model explained 41% of the variability in the data. Models that predict the dynamics of organism distribution and abundance enhance understanding of the temporal and spatial organization of ecological systems, as well as the decision‐making process in natural resource management.

Identifying Environmental Determinants of Diurnal Distribution in Marine Birds and Mammals

“…The timing of the transitions between habitat patches often depends on exogenous conditions. This is particularly true for marine birds and mammals, whose movements typically are influenced by environmental variables such as time of day, tide height, current speed, heat index, and wind speed (e.g., Delius, 1970;Galusha and Amlaner, 1978;Schneider and Payne, 1983;Stewart, 1984;Thompson et al, 1989Thompson et al, , 1997Watts, 1992;Henson et al, 2004;Hayward et al, 2005;Damania et al, 2005).…”

“…When temporarily disturbed by predators or humans, the abundance and distribution of marine animals in a system of habitat patches may recover rapidly relative to the rate of change of environmental variables (Henson et al, 2004;Hayward et al, 2005;Damania et al, 2005). That is, the environment may be assumed to remain constant while the system returns to its predisturbance state.…”

“…If we lump all noncensused locations into an (n + 1) st "habitat patch," then there are n(n + 1) = n 2 + n per capita flow rate functions r i j (i = j). Such models have been used to explain and predict the diurnal abundance dynamics of seabirds and seals (Henson et al, 2004;Hayward et al, 2005;Damania et al, 2005).…”

“…Models of this form have been used to predict the diurnal abundance dynamics of seabirds loafing on a pier (n = 1) (Henson et al, 2004), explain haul-out dynamics in seals (n = 1) , and model the diurnal movements of seabirds among four habitats at a Washington colony (n = 1, 2, 3) (Damania et al, 2005).…”

On the Dynamic Regulation of a Non Linear Model Fish Population

“…In the literature we find some mathematical models representing the dynamic evolution of certain renewable resources such as halieutic resources (Doubleday, 1975;Gouze, Rapaport, & Hadj-Sadok, 2000) and the animal resources (Damania, Phillips, Henson, & Hayward, 2005;. Using these models and some mathematical tools, we show that it is possible to analyze the dynamical evolution of certain renewable resources and to take decisions which help to protect our natural resources.…”