Individual study: Effect of mowing pattern on mortality of corncrake Crex crex chicks during mowing of hay and silage meadows in the Shannon Callows (County Offaly) and County Donegal, Ireland, and the Isle of Coll, Scotland
Tyler G.A, Green R.E. & Casey C. (1998) Survival and behaviour of corncrake Crex crex chicks during the mowing of agricultural grassland. Bird Study, 45, 35-50
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Use mowing techniques to reduce mortality
A replicated trial from 1992 to 1995 in Scotland and the Republic of Ireland (Tyler et al. 1998) found that a larger proportion of corncrake Crex crex chicks escaped when meadows were mown using a corncrake-friendly mowing pattern, where fields were mown from the centre outwards (inside-outwards) (68% of 76 chicks escaped) compared to the standard outside-inwards mowing pattern (45% of 31 chicks escaped). Fewer chicks were killed by inside-outwards mowing, even when the grass surrounding the plot being mown had already been cut. In plots mown from the inside-outwards, the proportion of chicks that escaped mowing declined as the distance to cover (vegetation over 20 cm tall) increased, and was higher for older chicks. Corncrakes were able to move away from the mower fast enough to escape mowing if an escape route to a refuge area was available, except for the youngest chicks (i.e. less than 2 days old). Hay and silage meadows in one area in Scotland were studied in 1994, and in two areas in Ireland from 1992 to 1995. Corncrakes were seen on a total of 59 meadows. Female corncrakes were radio-tagged to assess movement patterns. Fields were observed during both mowing patterns, and the number of chicks that escaped or were killed recorded. Meadows were searched following mowing to record the number of dead chicks and nest remains.
Use mowing techniques to reduce chick mortality
A replicated controlled study in three areas in Ireland between 1992 and 1995 (Tyler et al. 1998) found that corncrake Crex crex chicks were more likely to survive in hay and silage meadows when they were mown from the inside-out (I-O), compared to the traditional outside-in (O-I) mowing pattern (68% survival for 76 chicks in I-O fields vs. 45% survival for 31 chicks in O-I fields). Most chicks (80%) were killed during the last eight sweeps of the harvester for O-I and the last five for I-O, and mortality was zero for both methods when the nearest tall vegetation was within 5 m of the edge of the field. Chicks that were more than one day old were able to move fast enough away from the mower to escape, so long as a route to unmown cover was available.