SEASONAL DYNAMICS, MOVEMENTS AND THE EFFECTS OF EXPERIMENTALLY INCREASED FEMALE DENSITIES ON A POPULATION OF IMAGINAL CALOPTERYX-AEQUABILIS (ODONATA, CALOPTERYGIDAE)

Abstract. 1. A population of Calopteryx aequabilis Say was sampled daily on a tributary of Canard River, Kings County, Nova Scotia, for the entire flight season in 1983 (29 May to 13 August), using capture–mark–recapture techniques. 2. 2701 sightings of 678 individuals were obtained along a 635 m segment of the stream. A maximum daily count of 174 imagines was reached on 11 June, after which the population gradually declined. 3. More females than males were marked but sexually mature males outnumbered females at the water on all but four days. 4. Immigration rather than local emergence accounted for a large proportion of the population after 20 June. 5. Females were consistently vagile; males were site–specific but occasionally moved long distances between captures. 6. Males and females first marked as tenerals became reproductively mature after about 5 days. 7. We experimentally increased female density on a partially isolated section of the study stream to see how increased female numbers affected the demographics and movement patterns of the population. 8. Residence times for introduced and resident females were similar. In contrast, during a similar introduction of males a year earlier, most introduced males disappeared quickly. 9. Males decreased the distance they travelled daily between captures, their total distance travelled and their range following the introduction, and females showed a tendency (not statistically significant) toward increased movements and dispersal, as predicted. Copyright © 1990, Wiley Blackwell. All rights reserved