Impact of rainfall on the offspring PHA‐response and body mass in the Eurasian blue tit

Abstract

Animals are exposed to the more frequent stressful weather events that may impact parental decisions and their investment in offspring. This study examines whether and how heavy rainfall influences the birds' incubation behavior, hatching date, food volume brought to the nests, the offspring's immune response to phytohaemagglutinin (PHA) and their body mass during the post‐hatch period. The research was conducted on the Eurasian blue tits, Cyanistes caeruleus, living in a nest‐box area in the Niepołomice Forest (near Kraków, S Poland) during 3 years: 2009, 2010 and 2011. Rainfall did not directly affect the incubation period, but nestlings from eggs that incubated longer had a higher mass. Later hatching date was beneficial for the chicks' body mass, while earlier hatched chicks responded more efficiently to the PHA antigen. Although the intensity of rainfall did not directly affect the volume of food brought by adults to the chicks, its greater amount was beneficial for both indicators of their condition. With a more intensive rainfall, the weaker chicks responded to the PHA antigen, but achieved greater body mass. In the next years, it can be expected that heavy rainfall will become an increasingly important environmental cue, based on which birds will adapt their reproduction, and which will affect population trends, as the immune response weakened during the intensive rainfall is a survival indicator.

The Effects of Weather on Avian Growth and Implications for Adaptation to Climate Change

“…The effects of rainfall on nestling growth may depend on when rainfall occurs relative to a species' breeding season (Kruuk et al, 2015). During nestling growth, rainfall can decrease growth rates and age-specific morphometrics (Siikamäki, 1996;Kosicki and Indykiewicz, 2011;Kaspryzkowski et al, 2014;Pérez et al, 2016;Cox et al, 2019, but see Mainwaring andHartley, 2016;Grzędzicka, 2019; Table 2). Decreases in growth can result from nestlings having difficulty thermoregulating because of wet downy feathers or difficult foraging conditions for parents (Nye, 1964;Keller and Noordwijk, 1994).…”

The Impact of Weather on the Behavior and Ecology of Birds

“…The effects of rainfall on nestling growth may depend on when rainfall occurs relative to a species' breeding season (Kruuk et al, 2015). During nestling growth, rainfall can decrease growth rates and age-specific morphometrics Kosicki and Indykiewicz, 2011;Kaspryzkowski et al, 2014;Cox et al, 2019, but see Mainwaring andGrzędzicka, 2019; Table 2). Decreases in growth can result from nestlings having difficulty thermoregulating because of wet downy feathers or difficult foraging conditions for parents (Nye, 1964;Keller and Noordwijk, 1994).…”