Reproductive Strategies
The precise timing of reproduction is an important determinant of fitness of falcon. Increasing day length stimulates several neuroendocrine and endocrine secretions and triggers gonadal development in the anticipation of the breeding season. The female f
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Reproductive Strategies
2.1 The Breeding Life History Stage Reproduction is costly, and individuals that invest too much in a given reproductive bout pay with reduced reproductive output in the future (Sockman et al. 2006). Thus, the precise timing of reproduction is an important determinant of fitness (Davies and Deviches 2014). Overall, the reproduction of a falcon is not only dependent on food supply during the breeding period but also on conditions under which the partners lived before breeding (Cavé 1968). As well other vertebrates, falcons show an associated breeding life history stage where gonadal (see Box 2.1), territorial (see Chap. 3), mating (see Sect. 2.4), and parental (see Sect. 2.11) periods compose a long breeding season (Wingfield 2008). A developmental phase (see Sect. 2.2), when the reproductive system matures, preceded the mate choice (see Sect. 2.4), the nest choice (see Sect. 2.5), and the production (see Sect. 2.6) and incubation (see Sect. 2.8) of the eggs (Cade 1960; Wingfield 2008). The time lag between the start of reproductive development and the chick rearing phase forced parents to begin the developmental phase well before environmental conditions are optimal for feeding young (Thomson 1950; Davies and Deviches 2014). On the other hand against basic requirements for survival, a female must be in a suitable energetic state to initiate reproductive development (see Sect. 2.2) and egg formation (see Sect. 2.6.2; (Siivonen 1957; Drent 2006). Again, food availability plays a crucial role for the female state (Davies and Deviches 2014).
© Springer Nature Switzerland AG 2020 G. Leonardi, Behavioural Ecology of Western Palearctic Falcons, https://doi.org/10.1007/978-3-030-60541-4_2
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2 Reproductive Strategies
2.2 Developmental Phase 2.2.1 Photoperiod Photoperiod changes predictably and invariably between years. Breeding birds use day length as cue to broadly time their seasonal reproduction, especially in temperate zones where there is a clear distinction of day length in different seasons (Wingfield 2008). In fact, increasing day length stimulates several neuroendocrine and endocrine secretions (see Box 2.1) and triggers gonadal development in the anticipation of the breeding season (Lofts and Murton 1968; Wingfield 2008). Thus, hormones are secreted into the general circulation and stimulate gametogenesis and production of gonadal steroids (e.g., oestradiol and testosterone). As consequent, falcons excreted higher concentrations of faecal E (oestrogens), P (progestogens), and T (testosterone) during the breeding season than the non-breeding season (Staley 2003). Photoperiod is also the major regulator of haematocrit changes in falcons, but its control decreases 2 months before the onset of egg-laying (Rehder and Bird 1983). The timing of egg-laying of captive pairs was similar to the dates when eggs were found in the nests of wild falcons, but, under advanced photoperiod, these latter ones were induced to lay early (Nelson 1972; Olsen and Olsen 1980; Meijer et al. 1992).
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