Godwit chicks that grow up in a monoculture of grass – without herbs or flowers – grow less swiftly than chicks in ‘old-fashioned’, herb-rich meadows. This slow growth may contribute to the much lower chances of survival of those godwit chicks. Chicks that grow up on modern, intensively worked land that only has grass are two and a half times less likely to survive their first year of life than chicks that hatch on a herb-rich meadow. Ecologist Rosemarie Kentie and colleagues of the University Groningen have written about this in the last issue of the Journal of Applied Ecology.
Between 2007 and 2010, the researchers fitted a large number of godwit chicks with coloured rings to enable identification at a distance. Afterwards, several chicks were caught again and weighed to measure their growth. Notes were also taken of how many birds returned to the breeding grounds in subsequent years.
Of the birds who survived the first 25 days and fledged, the chicks from the intensively farmed land were on average 15% lighter than those that grew up on herb-rich grasslands. In addition, their beaks were 4% shorter, an indication of retarded growth. The chances of surviving the first year for a chick hatched on herb-rich land were 14%. A chick from the ryegrass monoculture only had a 6% chance. Most deaths occurred before the chicks fledged.
The researchers think that the chicks on intensive farmland suffer from a shortage of food, among other things. The quick growth of the thick grass means it’s harder for them to find insects. Further, once the grass in a modern meadow has been mown, they become easy prey for a range of predators in that shaven ‘grass desert’. Their slower growth also puts them at a disadvantage during the migration to and from West Africa.
A 14% chance of becoming an adult bird the next year does not seem very high. Nevertheless, the researchers write that it is probably high enough to maintain godwit numbers. When the chance drops to 6%, however, as it has in nearly all modern farmland, then the population will shrink.
‘Current policy concerning protection of meadow birds concentrates too much on protecting the nests and not enough on the growing chicks’, says Kentie. ‘If you continue only to stimulate breeding on intensive farmland by protecting nests, you may even be lowering the chances for the population as a whole. You are then protecting nests which produce too few young that grow to adulthood, and the parent birds will continue to return to the same nesting site in subsequent years. It would be much more effective to offer meadow birds sufficient herb-rich breeding grounds with a later mowing date, as well as protecting their nests.’
The research was conducted by the Department of Animal Ecology of the Centre for Ecological and Evolutionary Studies (CEES) of the University of Groningen. A primary source of funding was the Kenniskring Weidevogels (Meadow Birds Knowledge Group) of the former Ministry of Agriculture, Nature and Food Quality.
For more information:
• Rosemarie Kentie, University of Groningen, 0222-369 300
• Jos Hooijmeijer, University of Groningen
• Theunis Piersma, University of Groningen, 0222-369 300
Intensified agricultural use of grasslands reduces growth and survival of precocial shorebird chicks , Journal of Applied Ecology, 2 January 2013
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