Variation in ectoparasitic sheep tick Ixodes ricinus infestation on European Golden Plover chicks Pluvialis apricaria and implications for growth and survival
2019
Douglas, David J. T. | Pearce-Higgins, James W.
Tick infestation increased with temperature and vegetation height, and was negatively correlated with Golden Plover Pluvialis apricaria chick survival, but not growth rates. To examine the factors associated with tick loads on Golden Plover chicks and whether tick loads correlated with the growth rate or short-term survival probability. Twenty-one chicks from eight broods were radio-tagged and recaptured at 4-day intervals to measure tick loads, growth rate and determine survival probability between recaptures. All broods and 90% of chicks (19/21) had ticks present during at least one recapture, and ticks were present on 81% (70/86) of all recaptures. Mean tick load per capture was 9.2 (range 0–45) which was 13 times higher than the only previous comparable study on wader chicks. Tick loads were highest in warmer weather and when chicks moved through areas with taller average field layer vegetation. Tick loads were also correlated with chick age and date. The chick growth rate was highest in warmer weather and at mid-altitudes (400–450 m) but showed no significant correlation with tick load. The probability of a chick surviving between recaptures was positively correlated with chick body condition and negatively correlated with tick load. This study, albeit from one site and with small sample size, recorded high tick loads on Golden Plover chicks. Although unrelated to growth rates, ticks were negatively correlated with chick survival. Further work to identify the mechanism(s) underpinning associations between tick load and survival is required. Prior to considering whether tick control is an effective and justified management for wader conservation, research should first establish whether chick mortality from ticks limits Golden Plover and other wader populations on moorland.
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