While seabird–fishery associations are well documented, this research primarily comes from ship-based surveys and consequently individual level responses to discard availability are largely unknown. As part of a long-term study on lesser black-backed gulls (Larus fuscus) in the Netherlands, the fine-scale movements of adults were tracked with GPS tags throughout the breeding period. The aim of this study was to determine if lesser black-backed gulls were utilizing fishery discards in the Wadden Sea and to examine possible consequences of this behaviour. Within the Wadden Sea during weekdays, tracked birds predominately associated with zones where fishing vessels are known to operate (deep gullies). Across all individuals combined (n = 40), there was a significantly reduced use of the Wadden Sea during weekends when the fleets were not operating. Eight females, who markedly increased their use of the Wadden Sea during weekdays throughout the breeding period, were largely responsible for this pattern. The loss of discard resources on weekends primarily resulted in these eight individuals switching to terrestrial foraging areas. Nest attendance and total foraging time were consistent between weekdays and weekends, suggesting that resource shifts on weekends did not impact daily time budgets. As such, it appears that lesser black-backed gulls specializing on discard utilization are able to flexibly respond to the temporary loss of discards by switching to alternative resources.
Plastic pollution is an anthropogenic stressor in marine ecosystems globally. Many species of marine fish (more than 50) ingest plastic debris. Ingested plastic has a variety of lethal and sublethal impacts and can be a route for bioaccumulation of toxic compounds throughout the food web. Despite its pervasiveness and severity, our mechanistic understanding of this maladaptive foraging behaviour is incomplete. Recent evidence suggests that the chemical signature of plastic debris may explain why certain species are predisposed to mistaking plastic for food. Anchovy ( sp.) are abundant forage fish in coastal upwelling systems and a critical prey resource for top predators. Anchovy ingest plastic in natural conditions, though the mechanism they use to misidentify plastic as prey is unknown. Here, we presented wild-caught schools of northern anchovy () with odour solutions made of plastic debris and clean plastic to compare school-wide aggregation and rheotactic responses relative to food and food odour presentations. Anchovy schools responded to plastic debris odour with increased aggregation and reduced rheotaxis. These results were similar to the effects food and food odour presentations had on schools. Conversely, these behavioural responses were absent in clean plastic and control treatments. To our knowledge, this is the first experimental evidence that adult anchovy use odours to forage. We conclude that the chemical signature plastic debris acquires in the photic zone can induce foraging behaviours in anchovy schools. These findings provide further support for a chemosensory mechanism underlying plastic consumption by marine wildlife. Given the trophic position of forage fish, these findings have considerable implications for aquatic food webs and possibly human health.
In long-lived species, care-giving parents are expected to balance their own condition with that of their offspring. Many species of seabirds display a unique behavioural adaptation for managing these conflicting demands known as dual foraging, in which long trips, largely for self-maintenance, are alternated with short trips, which are primarily for offspring care. While dual foraging is a widely studied behaviour, it entails a complication that is seldom discussed: if parents independently employ a dual foraging strategy, chicks might be abandoned for extended periods when the long trips of both partners coincide. Whether partners coordinate their dual foraging strategies, however, is largely unknown. To investigate this possibility, we used radio frequency identification readers coupled with passive integrated transponder tags to record extended sequences of foraging trips for breeding Manx shearwaters Puffinus puffinus. Our results show a pattern of foraging trips that indicates a high level of coordination between parents, which facilitates consistent provisioning. Additionally, we show that the propensity for pairs to coordinate declines across the chick rearing period. Given the potential costs of not coordinating, we expect this behaviour to be widely spread among dual foraging species.
Although mechanisms of genetic and social inheritance have been implicated in determining the migratory routes of birds, it is unclear what their relative contributions are in species where outbound and return migration routes differ (‘loop migrants’). Here, we used biologging devices to follow Manx Shearwaters Puffinus puffinus, a long‐lived seabird with a trans‐Atlantic loop migration, from before their first migration until their 3rd calendar year. We found that Shearwaters undertake first migration without their parents, setting off almost immediately upon fledging and moving along a more direct trajectory than adults, before wintering in the same part of the South Atlantic as adult conspecifics and subsequently iteratively developing their return migration route over the next 3 years, each time returning – unlike adults – via a Western Atlantic route. We propose that the first outbound migration in Manx Shearwaters is broadly consistent with a genetically inherited vector, that both the outbound and the return migration trajectories are unlikely to be learnt from experienced conspecifics, and that return migration in Manx Shearwaters (and perhaps loop migrants more generally) may be informed by genetically inherited information and/or local environmental conditions.
A checklist of 864 plant taxa representing 355 genera and 93 families is given for the Karoo National Park. A total of 121 species are endemic to the Nama-Karoo, with Asteraceae the most common with 33 taxa. followed by Mesembryanthemaceae with 26 taxa. Phytochorological affinities indicate that 19.8% of the species are from the Nama- Karoo Biome only, another 19.8% are distributed over two biomes, and 41% of the species have a widespread distribution. The Karoo National Park conserves 30% of the recognized endemics of the Nama-Karoo Biome.
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