The Eurasian Collared-Dove Invasion in California: Has it Peaked?

Abstract

The invasion by Eurasian Collared-Doves of North America has been characterized by very rapid spread and initial exponential growth as this species colonized new areas. The recent occurrence and rapidity of this invasion have given ornithologists an ideal opportunity to study population dynamics of an exotic species. Some groups have developed predictive models of dispersal and population growth that can be tested using subsequent data from the invasion. Recent reports from the southeastern U.S. where the invasion first began suggesting that populations there have peaked and now seem to be declining. Even in California, where the doves arrived relatively recently, there are now reports of localized declines.         
I used Christmas Bird Count (CBC) data from 84 California Count Circles from eight different regions of the state and statewide Breeding Bird Survey (BBS) data to assess recent population dynamics and examine qualitatively how those dynamics compare to the model predictions for this species. CBC data from all eight regions and statewide BBS data 
suggest that the Eurasian Collared-Dove population in California has reached or is reaching a peak. Some areas, particularly in the northernmost parts of the state, showed patterns that suggest a declining population. These patterns are discussed in the context of the predictions of some of the models proposed for Collared-Dove population dynamics.