The Woodpecker's Cavity Microenvironment: Advantageous or Restricting?

Abstract

We studied the nesting biology of the Syrian woodpecker (Dendrocopos syriacus) in Israel, emphasising its physiological aspects and the environment of the tree hole nest cavity (~2 litres in volume). Eggs (mean mass = 5.4 ± 0.4 g SD) are laid once a day during April and May to produce a mean clutch size of four (range 3-5). Active incubation starts after the last egg is laid and lasts 11 days. Both hatching and fledging are spread over 2-3 days. Parents share incubation during the day but only males incubate at night. Both parents share the feeding of the nestlings equally. Males occupy and guard the empty nest at night all year round. Incubation and fledging periods add up to a normal fledging time for the species. The young are fed by their parents outside the nest for another month.Mean egg temperature was not significantly different between day and night, averaging 34.2ºC (± 4.3 SD). Mean egg water loss was 1.4 % d -1 of the initial egg mass prior to the onset of incubation and 0.5% d -1 during incubation. The extrapolated total water loss of the eggs was 13.1% at the end of incubation. This indicates a good match of cavity humidity and the water vapour eggshell conductance of 1 mg·(d Torr) -1 (=100 mg·(d kPa) -1 ), where, in spite of the higher egg temperature during active incubation, the egg water loss rate is reduced due to the presence of the incubating parent.Gas composition at the bottom of the nest initially decreased by ~1.75 % for O 2 whereas CO 2 increased by ~1.20 %, due to clutch activities until the nestlings were about 15 days old. There was little change in nest gas composition between 15 and 22 days of rearing. From that time on until fledging O 2 concentration increased and CO 2 decreased due to nestlings' up and down activity in the nest shaft and the fact that they fledge asynchronously at the age of 26 days.

The reproductive biology of the Syrian Woodpecker Dendrocopos syriacus in a newly colonized area of south-eastern Poland

“…The length of the egg-incubation period for the Syrian Woodpecker study population was similar to the corresponding length for populations in other, warmer regions of the range of this species: it averaged 11 days and ranged from 9 to 14 days (Ruge 1969;Marisova and Butenko 1976;Barnea 1982;Cramp 1985;Mersten-Katz et al 2012). The time that young Syrian Woodpeckers in the study population spent in the nest was quite similar to the corresponding time recorded for the Austrian population, where it was about 24-26 days (Ruge 1969;Holzer and Holzer 1982).…”

How does The Bird-nest Incubation Unit Work?

“…Data collected from the five species studied to date confirm that oxygen concentration is reduced and that of carbon dioxide is increased relative to ambient, with changes being moderate (1-2%) towards the end of incubation (Birchard et al, 1984;Lill and Fell, 2007;Mersten-Katz et al, 2013). The movement of the bird in and out of the nest chamber appears fundamental in ensuring that there is frequent exchange of gases within the nest (Mersten-Katz et al, 2013). A failure to introduce fresh air could lead to hypoxia, which may have important adverse effects on the survival of the incubating adults (Mersten- Katz et al, 2013) and their embryos (Tullett and Deeming, 1982).…”

“…The movement of the bird in and out of the nest chamber appears fundamental in ensuring that there is frequent exchange of gases within the nest (Mersten-Katz et al, 2013). A failure to introduce fresh air could lead to hypoxia, which may have important adverse effects on the survival of the incubating adults (Mersten- Katz et al, 2013) and their embryos (Tullett and Deeming, 1982).…”

Microclimate of Tree Cavities Used by Great Tits (Parus Major) in a Primeval Forest

“…Tree cavities effectively buffer eggs and chicks against ambient conditions, but they sometimes may become too efficient, and to hinder gaseous exchange (e.g. Ar et al, 2004;Mersten-Katz et al, 2012). This could create dangerous situations.…”

“…Data on microclimate in tree cavities occupied by breeding birds are rare Hooge et al, 1999;Martin and Ghalambor, 1999;Wiebe, 2001;Ar et al, 2004;Rhodes et al, 2009, Mersten-Katz et al, 2012. We presumed that different types of cavities would provide contrasting environments, but there are hardly any data to check this.…”