Tracking and retention time data from Larus fuscus feeding at Doñana ricefields in Andalusia

1. Non-frugivorous waterbirds disperse a wide variety of plants by endozoochory, providing longer dispersal distances than other mechanisms. Many waterbirds visit both agricultural and natural landscapes during their daily movements, but potential bird-mediated dispersal of weed plants within and from agricultural landscapes to other habitats is commonly overlooked. Gulls (Laridae) are expanding in numbers and increasingly exploiting anthropogenic habitats worldwide, with possible growing implications for the spread of weeds. Yet, to date there are no studies on the spatial distribution of weed dispersal by waterbirds.

2. We developed a plant dispersal model based on movements of 19 Larus fuscus using ricefields, via GPS telemetry. We combined daily movements with two curves estimating the retention times (RT) of plant seeds in their guts: 1) an experimental curve based on RT in captivity for four weeds with dry fruits known to be dispersed by gulls: Juncus bufonius, Cyperus difformi...