APPENDIX: GLOSSARY OF TERMS

Greek alphabet:

α: Maximum rate of egg production per female cowbird, in eggs/(cowbird*day).

β: Rate per female cowbird {nests/(cowbird*day)} at which nests are located by watching host parents, or by any means where rate does not vary with nest availability (N, which see).

β_i: Rate per female cowbird {nests/(cowbird*day)} at which nests of species i are located by watching host parents, or by any means where rate does not vary with nest availability (N, which see).

β_i: Vector consisting of the scalar finding rates β_i for all species i within the set I of host species in a community.

γ: Average rate (per cowbird) at which an individual female locates available host nests per unit of nest availability (N, which see). Units for γ are (nests located*ha)/(nests initiated*cowbirds).

γ_i: Average rate (per cowbird) at which an individual female locates available nests of host species i per unit of nest availability (N, which see). Units for γ_i are (nests located*ha)/(nests initiated*cowbirds).

δ: Exponential rate of decrease in cowbird fledging success with increasing level of parasitism.

Roman alphabet:

C: (Cowbird density): Number of breeding female cowbirds per unit area of breeding habitat in cowbirds/ha.

E_c: Rate per female cowbird at which cowbird eggs are laid.

Edge effect: Changes in community composition, abundances of individual species, and/or activity patterns of individual species as function of distance to an ecotone. Effects may include changes in avian breeding density, levels of nest predation, and levels of brood parasitism in proximity to edge.

F_c: Rate per female cowbird of cowbird fledgling production.

f_i: Rate {in nests/(cowbird*day)} at which an individual cowbird locates nests of species i.

Forest opening: Any of several thousand small disturbances maintained in the Hoosier National Forest by the Department of Natural Resources.

Functional response: A change in number of prey consumed per predator (or number of eggs laid in nests per cowbird) caused by a change in the density of prey (or hosts). Such changes can occur over both spatial and temporal gradients.

g_i: Probability that an individual cowbird will attempt to parasitize a nest of species i, given that she locates it.

h_i : Probability that an individual cowbird will successfully parasitize a nest, given that she attempts to do so. "Successfully parasitize" means that she is not deterred by aggression from the host parents, she is able to lay an egg in the nest, and the egg is not ejected by the hosts.

I: The set consisting of each host species i within the community.

j: Among host species whose nests cowbirds attempt to locate in a given avian community, species for which host quality is lowest.

K: The set of host species k that yield a greater parasitism payoff (which see) than species j (which see).

L: The set of host species l that yield a greater search payoff (which see) than species j (which see).

Landscape: An area of land (e.g., the Pleasant Run Unit of the Hoosier National Forest and surrounding forests) in which patches within the landscape vary in successional state and species composition.

Landscape context: The vegetative structure of lands surrounding a specified site.

Landscape pattern: A pattern of heterogeneity (e.g., in vegetative structure, parasitism level, etc.) within a landscape.

Level of parasitism: The intensity with which a host population is parasitized by cowbirds, often measured as the proportion of nests parasitized. In many situations a more useful measure is the mean number of cowbird eggs laid per host nest (including both parasitized and unparasitized nests). In the models described herein I define "level of parasitism" as P/N, which may be measured as cowbird eggs per nest over time intervals where P and N are constant.

N (nest availability): Instantaneous rate per unit area at which host nests become available for parasitism, in nests/(ha*day).

N_c: Critical value of nest availability (N) where the value of P under the egg-limitation model [Eq. (1)] is equal to the value of P under the finding-rate limitation model [Eq. (3)]. At levels of N below this value the finding-rate limitation model applies; at levels of N above this value the egg-limitation model applies.

n_i: Instantaneous rate per unit area at which nests of host species i become available for parasitism, in nests/(ha*day).

Numerical response: Change in the population density of predators (or cowbirds) with a change in the density of prey (or hosts). Such changes can occur over both spatial and temporal gradients.

P: Instantaneous temporal rate per unit area at which cowbird eggs are laid in nests of all host species, in eggs/(ha*day).

Parasitism payoff (h_iq_i): Index of fitness benefit to female cowbird of parasitizing a nest of host species i, given that she has located it. Index used herein is h_iq_i (see definitions of individual variables), which has units of fledglings/egg.

p_i: Instantaneous temporal rate per unit area at which cowbird eggs are laid in nests of a single host species i, in eggs/(ha*day).

Pseudo-numerical response: A functional response to nest density that involves changes in spatial patterns of activity within the home ranges of predators and/or cowbirds; but not involving true change in population densities of predators and/or cowbirds. Pseudo-numerical response can occur over both spatial and temporal gradients.

Q: Proportion of cowbird eggs laid in otherwise unparasitized host nests of all species that fledge cowbirds.

q_i (host quality): Relative quality of host species i in terms of the fitness gain a female cowbird obtains from parasitizing a nest of species i. Index used herein is the ratio of cowbird fledglings produced to cowbird eggs laid in singly-parasitized nests of species i, in units of fledglings/egg.

r: Mean area of breeding home range for female cowbirds, in ha.

Search payoff (h_iq_i/s_i): Index of fitness benefit to a female cowbird gained by searching for a nest of host species i, relative to the benefit of searching for nests of other species. Index used herein is h_iq_i/s_i (see definitions of individual variables), whose units are fledglings/(egg*day).

Source: A patch in which annual recruitment to a breeding population exceeds annual mortality.

s_i: Time required for a female cowbird to locate a nest of species i while she is actively searching. Units for this variable are days (to be consistent with other variables in equations), although typically time would be measured in minutes or hours (because it only includes time spent searching).

Structure-directed response: An activity pattern of a predator or a cowbird oriented with respect to the presence of ecotonal habitat (or some other structural feature), as opposed to a response oriented with respect to a gradient in nest density.

T: Proportion of the total time available to a cowbird (i.e., 24 h) that is spent nest-searching. This quantity is unitless.

t_i: Proportion of the total time available to a cowbird (i.e., 24 h) that is spent searching for nests of species i. This variable is unitless.