Shorebirds as important vectors for plant dispersal in Europe

Abstract

Shorebirds (Charadriiformes) undergo rapid migrations with potential for long‐distance dispersal (LDD) of plants. We studied the frequency of endozoochory by shorebirds in different parts of Europe covering a broad latitudinal range and different seasons. We assessed whether plants dispersed conformed to morphological dispersal syndromes. A total of 409 excreta samples (271 faeces and 138 pellets) were collected from redshank Tringa totanus, black‐winged stilt Himantopus himantopus, pied avocet Recurvirostra avosetta, northern lapwing Vanellus vanellus, Eurasian curlew Numenius arquata and black‐tailed godwit Limosa limosa in south‐west Spain, north‐west England, southern Ireland and Iceland in 2005 and 2016, and intact seeds were extracted and identified. Godwits were sampled just before or after migratory movements between England and Iceland. The germinability of seeds was tested. Intact diaspores were recovered from all bird species and study areas, and were present in 13% of samples overall. Thirteen plant families were represented, including Charophyceae and 26 angiosperm taxa. Only four species had an ‘endozoochory syndrome’. Four alien species were recorded. Ellenberg values classified three species as aquatic and 20 as terrestrial. Overall, 89% of seeds were from terrestrial plants, and 11% from aquatic plants. Average seed length was higher in redshank pellets than in their faeces. Six species were germinated, none of which had an endozoochory syndrome. Seeds were recorded during spring and autumn migration. Plant species recorded have broad latitudinal ranges consistent with LDD via shorebirds. Crucially, morphological syndromes do not adequately predict LDD potential, and more empirical work is required to identify which plants are dispersed by shorebirds. Incorporating endozoochory by shorebirds and other migratory waterbirds into plant distribution models would allow us to better understand the natural processes that facilitated colonization of oceanic islands, or to improve predictions of how plants will respond to climate change, or how alien species spread.

Seed mass, hardness, and phylogeny explain the potential for endozoochory by granivorous waterbirds

“…Migratory waterbirds such as ducks, shorebirds, and gulls disperse a broad range of angiosperms and other plants with propagules capable of surviving passage through the avian gut (i.e., through "endozoochory", Green et al 2016;Lovas-Kiss, Sanchez, et al, 2018b;Lovas-Kiss, Vizi, Vincze, Molnár, & Green, 2018a;Lovas-Kiss et al, 2019;Reynolds & Cumming 2016a). Recent models confirm that these birds are major vectors for long-distance dispersal (LDD), and angiosperm seeds are often moved over hundreds of km within the digestive tract of waterbirds such as granivorous dabbling ducks Anas spp.…”

“…(Farmer, Webb, Pierce, & Bradley, 2017;Kleyheeg et al, 2019;Reynolds & Cumming, 2016b;Viana, Santamaría, Michot, & Figuerola, 2013). Waterbird endozoochory has now been demonstrated for a variety of terrestrial and aquatic plants that lack a fleshy fruit, although this does not coincide with the dispersal syndromes often assigned based on seed morphology (Bartel, Sheppard, Lovas-Kiss, & Green, 2018;Lovas-Kiss, Sanchez, et al, 2018b;Lovas-Kiss et al, 2019;Lovas-Kiss, Vizi, et al, 2018a). This is a form of "nonclassical endozoochory," as it does not coincide with the "endozoochory syndrome" (Green, Elmberg, & Lovas-Kiss, 2019).…”

“…So far, our understanding of which plant species are dispersed by endozoochory by migratory waterbirds is limited by a general lack of empirical studies. However, those available show that plant species dispersed are associated with a range of terrestrial and wetland habitats and cannot be adequately predicted by simple classifications such as those commonly used to identify putative dispersal syndromes based on visual inspection of seed morphology(Bartel et al, 2018;Lovas-Kiss et al, 2019;Lovas-Kiss, Vizi, et al, 2018a;Soons et al, 2016). Indeed, this failure is inevitable since, by definition, no plants lacking a fleshy fruit can be assigned to the "endozoochory syndrome"(Pérez-Harguindeguy et al, 2013).…”

Zooplankton Diversity and Dispersal by Birds; Insights From Different Geographical Scales

“…For long-distance dispersal (LDD), Green and Figuerola (2005) in their thorough review of bird-mediated dispersal of zooplankton states that "... studies of LDD in aquatic systems remain in their infancy". Recent studies addressing the role of waterfowl and shorebirds for seed dispersal confirm a strong potential of endozoochory over short to moderate (< 20 km) distances (Bartel et al, 2018), but also long-distance dispersal across Europe (Lovas-Kiss et al, 2018). While it could be argued that plant seeds have a higher likelihood of being ingested and dispersed than aquatic animals, also resting stages of zooplankton may withstand gut passage.…”

Temporal development of biodiversity of macrophytes in newly established lakes

“…Instead, species development in the lakes is dependent on dispersal sources, which include species growing in streams and lakes hydrologically connected to the new lake (Nilsson et al, 2010;Soons et al, 2017), and species growing in freshwater bodies within a suitable distance for transfer by foraging birds (Brochet et al, 2009;Lovas-Kiss et al, 2019). As some lakes are re-established on former lake beds, it is also possible that seeds or spores of macrophytes in the flooded soils might still be viable (Alderton et al, 2017).…”