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 of plant seeds in their guts: (a) an experimental curve based on retention time in captivity for four weeds with dry fruits known to be dispersed by gulls: Juncus bufonius, Cyperus difformis, Polypogon monspeliensis and the alien Amaranthus retroflexus; (b) a theoretical curve based on the interspecific scaling relationship between body mass and mean retention time.
3. Median dispersal distances of weed plant seeds by gulls ranged between 690 and 940 m, but maximum distances exceeded 150 km. The theoretical retention time model showed higher median dispersal distances than the experimental retention time model. Spatial patterns of weed deposition were very similar between retention time methods, and most strongly depended on gull movements. Variation between individual gulls had little influence on seed shadows. About 92% of all seeds (>10,000 intact seeds per day) were dispersed within the ricefield area of 370 km². The remaining 8% of seeds were deposited beyond ricefields into other habitats, 42% of which reached moist environments (other irrigated agriculture, rivers and natural wetlands) presumably suitable for weed establishment.
4. Synthesis. Gulls can disperse weed plants over long distances across a mosaic of habitats. This implies exchange of weed plant species between human‐dominated and natural areas by waterbirds as dispersal vectors. This spatial study highlights the importance of non‐frugivorous birds for long‐distance plant dispersal, which is generally an overlooked mechanism in studies aiming to predict and manage expansion of weed plants.

中文翻译：

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农业景观内外越冬海鸥驱散杂草的空间格局

1. 非节食性水鸟通过内吞传播了各种各样的植物，比其他机制提供了更长的传播距离。许多水鸟在日常活动中会同时访问农业景观和自然景观，但是通常会忽略潜在的鸟类介导的杂草在农业景观内以及从农业景观到其他栖息地的扩散。海鸥（Laridae）的数量正在扩大，并且在全球范围内不断开发人类活动的栖息地，这可能对杂草的传播产生越来越大的影响。然而，迄今为止，还没有关于水鸟散布杂草的空间分布的研究。
2. 我们通过GPS遥测技术，利用稻田中19尾红us的运动，开发了一种植物扩散模型。我们将每日运动与两条曲线结合起来，以估计植物种子在其内脏中的停留时间：（a）基于被囚禁的四种杂草与已知由海鸥分散的干果的杂草在囚禁中的保留时间的实验曲线：Juncus bufonius，香附子，Polypogon monspeliensis和外来的Amaranthus retroflexus ; （b）基于体重与平均保留时间之间的种间比例关系的理论曲线。
3. 杂草植物种子通过海鸥的中位扩散距离介于690和940 m之间，但最大距离超过150 km。理论保留时间模型显示出比实验保留时间模型更高的中值分散距离。在保留时间方法之间，杂草沉积的空间模式非常相似，并且很大程度上取决于海鸥的运动。各个鸥之间的变化对种子阴影影响很小。大约92％的种子（每天> 10,000个完整种子）分散在370 km ²的稻田中。其余8％的种子沉积在稻田以外的其他生境中，其中42％达到了潮湿的环境（其他灌溉农业，河流和天然湿地），大概适合杂草的生长。
4. 综合。海鸥可以在杂草丛生的植被中长距离散布杂草。这意味着水鸟作为散布媒介在人类控制的区域和自然区域之间交换杂草植物物种。这项空间研究突显了非节食鸟类对长距离植物扩散的重要性，这在旨在预测和管理杂草植物扩展的研究中通常被忽视。