Data from: Agricultural pastures challenge the attractiveness of natural saltmarsh for a migratory goose

1. Broad-scale land conversions and fertilizer use have dramatically
altered the available staging area for herbivorous long-distance migrants.
Instead of natural land, these birds rely increasingly on pastures for
migratory fuelling and stopover, often conflicting with farming practices.
To be able to predict and manage birds’ future habitat use, the relative
advantages and disadvantages of natural (e.g. saltmarsh, intertidal)
versus anthropogenic staging sites for foraging need to be understood. 2.
We compared the migratory staging of brent geese on saltmarsh and pasture
sites in spring. Food quality (nitrogen and fibre content), intra-specific
antagonistic behaviour, and body weight were quantified at nearby sites in
simultaneous seasons. Individuals were tracked with high-resolution GPS
and accelerometers to compare timing of migration and time-budgets during
fuelling. 3. On pastures, birds rested more and experienced higher
ingestion rates, similar or superior food quality and reduced antagonistic
interactions than on saltmarsh. 4. Brent geese using fertilized grasslands
advanced their fuelling and migration schedules compared to those using
saltmarsh. Pasture birds reached heavy weights earlier, departed sooner,
and arrived in the Arctic earlier. 5. Intertidal mudflats were frequently
visited by saltmarsh birds during the day, and available food there
(algae, some seagrass) was of higher quality than terrestrial resources.
Availability of intertidal resources was an important factor balancing the
otherwise more favourable conditions on pastures relative to saltmarsh. 6.
Policy implications: Disadvantages of longer foraging effort, more
antagonistic interactions and delayed fuelling schedules on traditional
saltmarshes may cause a trend of geese exchanging this traditional niche
in favour of pastures, especially in a warming climate that requires
advancement of migratory schedules. However, the high quality of
intertidal forage allows it to complement terrestrial foraging,
potentially removing the incentive for habitat switches to pastures. The
relatively high quality of green algae and seagrass, and birds’ remarkable
preference for these resources when available, provides a key for managers
to create landscapes that can sustain this specialist’s intertidal
lifestyle. To keep natural habitats attractive to staging geese with the
purpose to prevent conflicts with farming practices, management actions
should focus on conservation and restoration of saltmarsh and especially
intertidal habitat.