Investigating the population dynamics of California spotted owls without marked individuals
- First Online:
- 298 Downloads
Understanding population dynamics is of great interest in many different contexts. Traditionally, population dynamics have often been considered in terms of individual-based demographic parameters (e.g., abundance, survival, and reproductive rates), estimation of which generally requires information from marked individuals. Alternatively, in some situations, it may be appropriate to consider population dynamics at a landscape level where the focus is shifted from numbers of individuals to the status of the population at places on the landscape. One consequence of doing so is that information from marked individuals is no longer required. Recently developed methods allow the estimation of landscape-level population vital rates in the realistic situation where the current status of the population might be misclassified via field methods (e.g., because of imperfect detection). Here, we consider the case of the California spotted owl (Strix occidentalis occidentalis) at the Eldorado study area in central Sierra Nevada, California, USA, where interest is in the occupancy rate of potential nesting territories, and in whether owls in an occupied territory successfully reproduced each year during 1997–2004. We analyzed the data using multistate occupancy models and found no evidence of annual variation in dynamic occupancy probabilities. There was strong evidence of annual variation in successful reproduction, with the pattern of variation being different depending on whether there was successful reproduction in the territory in the previous year. Of the three environmental variables considered, the Southern Oscillation Index appeared to be most important and explained some of the annual variation in reproduction probabilities.
KeywordsCalifornia spotted owl Detection Multistate Occupancy models
- Anthony RG, Forsman ED, Franklin AB, Anderson DR, Burnham KP, White GC, Schwarz CJ, Nichols JD, Hines JE, Olson GS, Ackers SH, Andrews LS, Biswell BL, Carlson PC, Diller LV, Dugger KM, Fehring KE, Fleming TL, Gerhardt RP, Gremel SA, Gutierrez RJ, Happe PJ, Herter DR, Higley JM, Horn RB, Irwin LL, Loschl PJ, Reid JA, Sovern SG (2006) Status and trends in demography of northern spotted owls, 1985–2003. Wildl Monogr 163:1–48Google Scholar
- Franklin AB, Gutiérrez RJ, Nichols JD, Seamans ME, White GC, Zimmerman GS, Hines JE, Munton TE, LaHaye WS, Blakesley JA, Steger GN, Noon BR, Shaw DWH, Keane JJ, McDonald TL, Britting S (2004) Population dynamics of the California spotted owl (Strix occidentalis occidentalis): a meta-analysis. Am Ornithol Union Monogr No 54:1–54Google Scholar
- MacKenzie DI, Nichols JD, Royle JA, Pollock KH, Bailey LL, Hines JE (2006) Occupancy estimation and modeling: inferring patterns and dynamics of species occurrence. Elsevier, San DiegoGoogle Scholar