Declining egg viability explains higher hatching failure in a suburban population of the threatened Florida scrub‐jay Aphelocoma coerulescens

Abstract

Hatching failure occurs in approximately 10% of all avian eggs, but varies both within and among species. This reduction in viable offspring can have significant fitness consequences for breeding parents; therefore, it is important to understand which factors influence variation in hatching failure among populations. Previous research suggests that hatching failure is higher in a suburban than in a wildland population in the Florida scrub‐jay. From 2003 to 2007, we performed two experiments to examine whether increased hatching failure in the suburbs resulted from 1) increased length of off‐bouts during incubation (predation risk hypothesis, 2003–2004) or 2) increased exposure to ambient temperature during laying (egg viability hypothesis, 2005–2007). Hatching failure was higher for females that took fewer off‐bouts, but the length of those off‐bouts did not influence hatching failure. Thus, nest predation risk does not appear to explain higher hatching failure in the suburbs. Alternatively, hatching failure increased with increasing exposure of eggs to ambient conditions during the laying period. First‐laid eggs in the suburbs had the greatest pre‐incubation exposure to ambient temperature and the greatest rate of hatching failure, consistent with the egg viability hypothesis. Urbanization influences hatching failure through a series of complex interactions. Access to predictable food sources advances mean laying date in suburban scrub‐jays, leading to larger clutch sizes. Because scrub‐jays begin incubation with the ultimate egg, first‐laid eggs in the suburbs may be exposed to ambient temperatures for longer periods, thus reducing their viability.

Wildlife Population Dynamics in Urban Landscapes

“…The curves are merely conceptual based on the literature and do not represent a formal meta-analysis. Curves exhibiting extreme changes in mortality rates (such as vehicles) represent the "strength" (or consistency) of the pattern among studies, whereas a slight curve (such as disease) reflects mixed results and a more complex relationship with urbanization in suburban areas (Schoech and Bowman 2003;Fleischer et al 2003), advanced laying dates resulted in greater hatching failures due to increased exposure of eggs to low ambient temperatures (Aldredge et al 2012). While most studies have demonstrated advanced phenology of residents and short-distance migratory birds in cities (Eden 1985;Antonov and Atanasova 2003;Schoech and Bowman 2003), urban birds also may initiate breeding later.…”

A review of urban impacts on avian life‐history evolution: Does city living lead to slower pace of life?

“…Rather than being affected by urbanization, CORT levels seem to be more dependent on species, sex, life-history stage, or even morphs studied. A good example to illustrate this lack of pattern comes from analyses of CORT levels in urban and rural house sparrows from three different cities: Phoenix (USA), Budapest (1998), Leston & Rodewald (2006), Marzluff & Neatherlin (2006), Rodewald & Shustack (2008a,b), Whittaker & Marzluff (2009) Laying date 10 (5) 7 (7) 3 (2) Eden (1985), Antonov & Atanasova (2003), Mennechez & Clergeau (2006), Hinsley et al (2008), Newhouse et al (2008), , Aldredge et al (2012), Stracey & Robinson (2012), Brahmia et al (2013), Strasser & Heath (2013), Solonen (2014), Solonen & Hilden (2014), Sumasgutner et al (2014), Lin et al (2015), Wawrzyniak et al (2015), Bailly et al (2016), Sprau et al (2016), Vaugoyeau et al (2016) attendance in eight different bird species, nest attendance was higher in four (Table S7), did not differ in three and was lower in one study with a small sample size (nine lesser kestrel, Falco naumanni nests, Liven-Schulman, Leshem, Alon, & Yom-Tov, 2004). This was sometimes associated with less quality food for offspring (e.g.…”

The effects of low levels of light at night upon the endocrine physiology of western scrub‐jays (Aphelocoma californica)

“…While observational and experimental work point toward the ready access of human‐source foods in the suburban environment as the primary driver of the earlier reproduction, numerous other factors might also contribute (Schoech and Bowman, ). Potential factors experienced in a suburban versus a natural habitat that could be stimulatory include increased: (1) temperature due to an “urban heat island” effect (e.g., Fan and Sailor, ; for site‐specific data see Aldredge et al, ); (2) predictability of food resources (i.e., knowing where food can be obtained at any time on a year‐round basis, such as a pet food dish, see Bridge et al, ); and (3) exposure to artificial lighting at night from street lamps and houses.…”