Artificially incubate eggs or warm nests

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

26%
Certainty

16%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

If incubating parents spend a long time away from the nest then the eggs may cool and potentially develop abnormally or die before hatching. For very intensively-managed species with very low populations, it may therefore make sense to warm eggs gently whilst parents are away from the nest.

Study locations

Key messages

A replicated, controlled trial in the UK found that great tits Parus major were less likely to interrupt their laying sequence if their nest box was heated, although there was no effect on egg or clutch size.
A small study in New Zealand found that no kakapo Strigopus habroptilus eggs or chicks died from chilling following the use of nest warmers. Before this a nest had been lost to chilling.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, controlled trial in 1991 in woodland in Oxfordshire, England (Yom-Tov & Wright 1993), found that blue tits Parus caeruleus nesting in heated nest boxes did not have significantly heavier eggs or larger clutches than those in unheated boxes. However, birds were less likely to interrupt their laying sequence in heated boxes (33% of 16 heated nests had interruptions vs. 67% of 14 unheated nests). Heat was provided by a small ‘night light’ candle, 8 cm below the bottom of the box, which raised the temperature in the box by an average of 6^oc, saving roosting blue tits approximately 0.77 kcal/night, comparable to 35% of the energetic cost of producing an egg.
Study and other actions tested
Referenced paper
Yom-Tov Y. & Wright J. (1993) Effect of heating nest boxes on egg laying in the blue tit (Parus caeruleus). The Auk, 110, 95-99.
A small study on Codfish Island, South Island, New Zealand (Jansen 2005) found that no kakapo Strigopus habroptilus eggs or chicks died from chilling between 1997 and 2005, following the use of specially designed nest heat pads to keep eggs and chicks warm while the female is off the nest. Before pads were used, a nest containing three eggs lost failed, apparently due to chilling of the eggs and chicks as the female spent large periods of time away from the nest.
Study and other actions tested
Referenced paper
Jansen W.P. (2005) Artificial incubation of kakapo Strigops habroptilus eggs and brooding of chicks while in the nest, Codfish Island, New Zealand. Conservation Evidence, 2, 6-7.

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2020) Bird Conservation. Pages 137-281 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Bird Conservation

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