Exotic birds show lags in population growth

Background/Question/Methods

A key aspect of the ecology and management of biological invasions is the prevalence and duration of lag phases in population growth. Lag phases can be shorter or longer than the early period of exponential growth, which emphasizes the need for increased predictive capabilities to inform management decisions. We expand on the use of piece-wise model fitting techniques to detect lags in exotic bird populations on Hawaii. 

Results/Conclusions

We found evidence of lag phases for 15 of 17 species we evaluated (range: 8 - 39 years, mean = 17). We evaluated the influences of body size, niche breadth, propagule pressure, length of record, and lag phase growth rate on the duration of these lags, but found no evidence for any association. Our results are the first to rigorously quantify lags in exotic animal populations; most existing evidence comes from plants. We show that lags are as common in birds as in plants, although we provide preliminary evidence that the duration of lags in birds is shorter than in plants. We highlight the need for continued efforts to elucidate lag phase occurrence and duration in biological invasions, and we demonstrate the expanded utility of piecewise model fitting approaches to quantify these lags.