Variable secuelas psicosociales de la violencia política

The breeding phenology of Cyprus Wheatear at Troodos Mountain showed clear seasonality patterns varying between years that arose mostly from variation in clutch initiation date at the start of breeding. Although the overall breeding cycle varied between years, once clutch initiation started the phenology was similar between years,

0 10 20 30 M a xi m u m d a il y te m p e ra tu re ( C )

MARCH APRIL MAY JUNE JULY AUG

2010 2011 2012

Chapter 2: Breeding Phenology

78 although differences were more pronounced for the period of post-fledged parental care. Significant variation between the three years for post fledged parental care were shown: during 2010 the species was found to care for fledglings for approximately one month in comparison to 2011-2012 when the period was for approximately two weeks. After the species started breeding and the first egg was laid, the duration of incubation and hatchling was fairly constant between years. Variation in the breeding phenology of the Cyprus Wheatear was predominantly determined by inter-annual variation in clutch initiation dates, renesting probability and the duration of parental care after chicks fledged.

The results showed that the singing activity of Cyprus Wheatear was high during the beginning of the season, during pair formation and before egg-laying but declined sharply thereafter (Figure 2.3). The seasonal pattern of singing observed in the current study is likely to reflect its function in mate attraction and retention. Singing clearly reflects breeding effort (see Chapter 5) and as such I demonstrated that its occurrence varied with year as we also demonstrated that other aspects of phenology such as clutch initiation date varied by year. Similar observations were made by Merila and Sorjonen (1994) studying the functions of male song in Bluethroat Luscinia svecica

svecica, by examining seasonal and diurnal patterns of song. They found that

seasonal patterns of singing activity peaked shortly after male arrival and before the onset of egg-laying. Similarly Lampe and Espmark (1987) showed when studying the function of song of Redwings Turdus iliacus throughout the breeding season, that the singing rate of breeding males decreased significantly when egg-laying started, whereas inter-seasonal variation of song was negligible.

Chapter 2: Breeding Phenology

79 Results indicated that clutch initiation date for Cyprus Wheatear varied across years, probably in response to temperature, and this variation consequently dominated the rest of the breeding phenology. The Cyprus Wheatear breeding phenology showed flexibility in response to warm and cold springs indicating that the species may adjust clutch initiation days to optimum food availability at least at Troodos, where first nest attempts were significantly later in the cold spring of 2011, compared to 2010 and significantly earlier in 2012 in a warm spring. The Cyprus Wheatear is a generalist insectivorous species that is likely to time its breeding to the availability of its insect food that will become more abundant as spring temperatures rise. Many migratory species, and particularly small passerine long-distance migrants such as wheatears use food resources on the breeding grounds for egg production: low temperatures on arrival may limit food availability and delay laying, and in contrast, with warmer springs, migrants may nest earlier (Ockendon et al. 2013). For example, in a long-term study of the migratory Pied Flycatcher, advances in egg-laying day correlated with advances in food availability (Both and Visser 2005). Visser et al. (2004) argued that climate change might lead to differential changes in the breeding dates and the time of maximum food abundance. As they showed in their paper Dutch Great Tits responded too weakly to climate change in comparison with a UK population (Cresswell and McCleery 2003), which showed better synchronization with their prey and overall flexibility to advance hatching in warm springs, and consequently to maintain breeding success over the years. Whether Cyprus Wheatears are modifying their clutch initiation date adaptively to their peak of food availability, if indeed such exists, remains to be investigated.

Chapter 2: Breeding Phenology

80 The duration of the egg stage for Cyprus Wheatear varied with year being significantly longer in 2011 than in 2010 a 2012 (Figure 2.5) suggesting that this too is responsive to conditions such as temperature and food availability. Both and Visser (2005) showed that Pied Flycatchers that breed earlier in warmer years reduce intervals between laying and hatching. In contrast, early laying Great Tits increase laying- hatching intervals (Cresswell and McCleery 2003). In both cases the birds were shown to be adaptively adjusting their hatch date to coincide with the peak of food availability for feeding chicks. The duration of the nestling stage showed little variation being about 2 weeks in duration in all cases. Predation pressure accounted for most if not all nest failures in our population and it is likely that fledging chicks as rapidly as possible is the best defence against this risk (see Chapter 4).

The duration of post-fledging parental care varied significantly depending on year and nest type, showing a decline through the season with date but with extended parental care during 2010 compared to 2011-2012 (Figure 2.6). Post-fledging care lasted on average for two weeks during 2011-2012 and for more than three weeks during 2010 (range 12-29 days), the latter being comparable with Northern Wheatears (Moreno 1984a). Such variation may arise through annual variation in food availability as shown with studies on Great Tits where food availability may determine the duration of post-fledging care (Higuchi and Momose 1981). The decision to terminate or extend the period of post-fledging care is unlikely to be independent of the decision to have a second brood. There is a trade-off between successive reproductive attempts, whereas, starting a second clutch reduces the reproductive value of the first clutch because of the effect of second clutches on post-fledging care (Verhulst et al. 1995). Verhulst and Hund (1996), observed that in species that initiate multiple broods in a

Chapter 2: Breeding Phenology

81 single season there is usually a trade-off between the number of young in the first brood, and the timing and occurrence of the subsequent broods. They studied the effect of second clutch on the post-fledging care in great tits and found that parental care continued for 20 days (range 10-32 days) after fledging but that second clutches reduced the females’ contribution to post fledging care. Husby et al. (2009) examined temporal population-level trends in the proportion of female Great Tits double- brooding, and found that the probability that a female produces a second clutch was related to the timing of first clutch relative to the peak in caterpillar abundances, and thus declined over the season. Key in these trade-offs is the length of the breeding season and also the length of the food peak available for the chicks. For example, in the Black Wheatear Oenanthe leucura, there were two variables which determined the number of breeding attempts: the date of onset of breeding and the intervals between raising a brood and laying another clutch (Soler et al. 1995). Late first broods and long periods of post fledging care because of low food availability may therefore prevent second broods.

Renesting probability declined through the breeding season in Cyprus Wheatears. This may reflect seasonal declines in the fitness of clutches. For example, Öberg et al. (2014) used long-term data on breeding time in Northern Wheatears to investigate seasonal declines in reproductive output. They suggested that degrading environmental conditions (i.e. reduction in food supply to feed chicks) together with effects of nest predation were the main determinants of the seasonal decline in fitness. Renesting probability differed significantly between years, with 2010 having the lowest renesting rate after success attaining very few second broods (Figure 2.8): this effectively resulted in that year being single-brooded and the other two years

Chapter 2: Breeding Phenology

82 being double-brooded. The implication is that environmental conditions were substantially different in 2010. As the temperature data showed, this was a particularly warm, early year suggesting that it may be high temperatures that affect availability of food for chicks in second broods.

Local ambient temperature patterns are likely to be the cue for Cyprus Wheatear breeding, and thus timing of their clutch initiation date and occurrence of post-fledging care period and a second brood – crucial life-history and population demographic traits for the species. With only three years’ data we can only speculate, but examination of Figures 2.8 and 2.9 suggest that early warm temperatures and later higher temperatures lead to a reduction in the probability of a second brood. Analyses of mean daily ambient temperature for April throughout August for the three years of the current study showed that 2010 was on average much warmer (by several degrees) although this difference was less pronounced later in the season. Studies on, for example, great tits have verified that first egg date (Forchhammer et al. 1998), clutch size (Perrins 1970), incubation date (Van Balen 1973) and hatch date (Winkel and Hudde 1997) all depend on the temperature. And other studies, for example Cresswell and McCleery (2003), have shown how Great Tits can very subtly adapt their schedules to intra- and inter-seasonal variation in temperature. In Cyprus Wheatears we have the likely confirmation of another facultative mechanism of optimising reproductive scheduling to ambient temperature conditions – highly variable periods of post-fledging care versus initiating a second brood.

The great flexibility of the species breeding under fluctuating ambient temperature suggests that they are already adapted to climate change, particularly with a seasonally dependent optimization of clutch initiation date and probability of second

Chapter 2: Breeding Phenology

83 broods on the basis of the temperatures being high during a season. There seems already to be an adaptation by the species to variable climate and so climate change. But there is a need for long term studies to test these hypotheses with more than N = 3 years of data. In particular I would predict that in early hot years there will be early initiation of breeding, extended post-fledging care and a low proportion of second broods.

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