Breeding black-tailed godwits affected locally by climate change

What is the effect of climate change on black-tailed godwits? This is what researchers from the University of Groningen and the University of Oxford asked themselves. Their conclusion is that it does affect them, but only in places where the quality of their breeding habitat – agricultural land – is poor due to deep drainage and frequent mowing and therefore a lack of flowers and insects.

Many species of birds are breeding earlier than 40 years ago. This is because food for their young is available increasingly early as spring comes earlier. Surprisingly, black-tailed godwits no longer appear to have adapted to this shift since 1980. This is strange because developments in dairy farming such as faster grass growth, and thus earlier mowing, mean that black-tailed godwits would benefit from breeding earlier. The grass is now growing faster because of agricultural intensification and because springs are warmer.

Laying date

The researchers from Groningen (Team Piersma) and Oxford examined data from the last 11 years. In cold springs, and on fields with the greatest diversity of plants and the highest water level, most eggs hatched and most hatchlings reached maturity.

Researcher Rosemarie Kentie, working at Oxford: ‘As we expected, it was clear that black-tailed godwits that nested early in spring had the most young. So, why don’t they lay their eggs sooner? First, we found no relationship between the laying date of the parents and the laying date of their young. This means that although black-tailed godwits that hatched from their eggs early had a greater chance of returning as a breeding bird in the years that followed, they did not lay their eggs earlier as a matter of course. Second, only experienced breeding birds appear to breed earlier if the spring is very warm and if they bred early the year before too. Thus, only experienced birds can manage to change the laying date. We therefore have not been able to discover how a bird becomes an early breeder.’

If the temperature keeps rising

As all climate predictions point towards further global warming, the researchers wanted to assess what the consequences could be. They predict that if the temperature in spring continues to rise at the same speed over the coming 40 years, black-tailed godwits will eventually breed five days earlier . These five days will not be enough to keep up with the predicted climate change in dry fields that are low in herbs and used for intensive agriculture, although they will be in flower-rich moist fields that are managed especially for meadow birds.

Kentie: ‘This research shows that loss of habitat quality and climate warming reinforce each other, and, if looking at the future, more account must be taken of this.’ For black-tailed godwits this means that herb-rich damp meadows will become even more important for the preservation of the species than they already are .

More information

Link to article on Global Change Biology.