Effect of intermittent incubation and clutch covering on the probability of bacterial trans‐shell infection

Abstract

Microbial infection is considered a critical cause of hatching failure in birds. Although several behavioural mechanisms are believed to improve reproductive success in birds, their direct effect on the risk of bacterial trans‐shell infection (BTSI) remains to be tested. Here, we focus on the protective roles of intermittent incubation and covering of the clutch with nest lining during the laying period, when eggs are highly susceptible to BTSI. To our knowledge, this study is the first to use culture‐independent PCR‐based methods to measure quantitative and qualitative indices of BTSI. In our experiment, we exposed Mallard Anas platyrhynchos eggs that were either intermittently incubated (I‐INCUB) or un‐incubated (I‐UNINCUB), and covered (COV) or uncovered (UNCOV) with nest lining. Hatchability of I‐INCUB eggs was twice that for I‐UNINCUB eggs. The presence and degree of BTSI had no effect on hatching success of experimental eggs. The residual weights of ducklings hatched from infected and I‐INCUB eggs were lower than those from uninfected and I‐UNINCUB eggs. In addition, ducklings originating from COV eggs were heavier than those hatched from UNCOV eggs. Intermittent incubation and clutch covering had no effect on the probability or degree of BTSI. Although the effect of BTSI is considered less detrimental in temperate birds, we show that the presence of BTSI inside the egg may significantly affect hatchling phenotype. This represents a novel insight into the role of BTSI in the reproductive success of birds and implies that the use of molecular PCR‐based methods is required in future studies for a better understanding of such causality.

Microbial Infections Are Associated with Embryo Mortality in Arctic-Nesting Geese

“…Recent results from a study using experimental mallard nests suggested that bacterial infection of waterfowl eggs may have no effect on hatchability (37). In contrast, our results provided evidence that bacterial infection is a mechanism of embryo mortality and may have been responsible for the elevated rates of nonviable eggs reported here.…”

“…Our identification of a Neisseria species as the predominant bacterium present in addled eggs appears to be novel, although species in the Neisseria genus have been associated with waterfowl on several occasions. Neisseria animalis was isolated from mallard (Anas platyrhynchos) eggs in the Czech Republic (37). Three isolates that most closely matched N. mucosa, N. canis, and N. meningitidis were isolated from duck feces in New Zealand (38), and N. animaloris was detected in the liver of a shelduck (Tadorna sp.)…”

“…Based on our inoculation study, postinoculation survival time was negatively related to inoculation doses, and some eggs infected at low doses did survive. Survival to hatching of bacteriainfected embryos has been observed in both captive and wild waterfowl (14,16,37,40), and surviving young can sometimes act as carriers of pathogenic bacteria (14,40). It is also possible that white-fronted goose eggs are more resistant to bacterial infection than the chicken eggs used in our study, or that our inoculation doses were higher than is typical in the wild.…”

Different incubation patterns affect selective antimicrobial properties of the egg interior: experimental evidence from eggs of precocial and altricial birds

“…Recent studies have found bacterial density on the eggshell to be the main precursor of hatching failure across avian species (Lee et al, 2017;Peralta-Sanchez et al, 2018;Tomas et al, 2018). These findings are not surprising given that previous studies documented that microbes are able to pass through the eggshell into the egg interior and negatively affect embryo viability (Bruce and Drysdale, 1994;Pinowski et al, 1994;Cook et al, 2003;Fonseca et al, 2011;Hansen et al, 2015) or hatchling phenotype (Javurkova et al, 2014).…”

Partial incubation during egg laying reduces eggshell microbial loads in a temperate‐breeding passerine

“…Hatchability across a range of avian taxa tends to increase with latitude (Koenig 1982), suggesting that factors promoting egg viability may be less strongly selected in temperate regions. Although exposure of eggs to ambient conditions without incubation in the temperate zone quickly reduced viability in some species (Veiga 1992, Godard et al 2007, Javŭrková et al 2014, viability decline was delayed in others (Arnold et al 1987, Arnold 1993, Walls et al 2011. Hatching success was not related to eggshell bacterial load during incubation (Ruizde-Castañeda et al 2011a, b, Walls et al 2012 or affected by cleaning with alcohol (Walls et al 2011).…”