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636 Hand-Rearing Birds

(McGraw 2004). Thus, there are still many questions remaining about the optimal level and type of
carotenoid that should be provided to chicks. Sources of dietary carotenoids include insects (natu-
rally enriched, or enriched via their feeding and/or gut-loading; Ogilvy et al. 2012; Finke 2015b),
produce items, or commercial supplemental forms (e.g. marigold extract, a source of the yellow
pigments lutein and zeaxanthin or canthaxanthin, a source of red pigmentation). Again, further
research is needed to characterize the optimal level of these pigments in avian diets, but the risk of
toxicity from these compounds is low.
As mentioned previously, it has also been suggested that the preference of Blue Tits (P. caeruleus)
for spiders during their nesting season may be due to their high levels of taurine (Ramsay and
Houston 2003). Supplementing the diet of wild Blue Tit nestlings from 2 to 12 days of age with
taurine resulted in juveniles that took significantly greater risks when investigating novel objects
and were more successful at a spatial learning task than controls (Arnold et al. 2007). Adult insects
and commercial cat/kitten foods are rich sources of taurine, while insect larvae and vegetable
protein-based commercial products (unless supplemented) would typically contain little taurine.

Conclusions

It is crucial to note that animals require nutrients and appropriate substrates to deliver those
nutrients, as opposed to specific diet ingredients. Thus, it is completely reasonable that insect-
substitute diets may serve as a complete diet item in a facility. Alternatively, commercially-avail-
able insects with appropriate supplementation may be more appropriate for a particular situation.
There are several options for feeding insectivorous nestling birds in rehabilitation settings. Each
comes with pros and cons, and institutions should determine what feeding program(s) best meet
their needs with regard to chick success, resource allocation (human and monetary), and availa-
bility of food items. It is likely that more than one option is optimal within an institution. Care
should be taken to document feeding programs, such that educated decisions about modifications
can be made for future improvements to protocols. Additionally, when utilizing recipes for insect
supplementation or for insect-substitute diets, it is critical to follow recipes precisely or the
intended nutritional profile may not be achieved. Ideally, nutrients are provided to chicks in a
way that is appropriate to their digestive physiology, nutrient needs for development of robust
immunity, skeleto-muscular systems, and neurological functions to provide optimal chances of
success post-fledging and release.

References

Arnold, K.E., Ramsay, S.L., Donaldson, C., and Adam, A. (2007). Parental prey selection affects
risk-taking behaviour and spatial learning in avian offspring. Proceedings of the Biological Society B
274: 2563–2569.
Aschoff, J. and Pohl, H. (1970). Rhythmic variations in energy metabolism. Federation Proceedings 29
(4): 1541–1552.
Barker, D., Fitzpatrick, M.P., and Dierenfeld, E.S. (1998). Nutrient composition of selected whole
invertebrates. Zoo Biology 17: 123–134.
Bartholomew, G.A. and Cade, T.J. (1963). The water economy of land birds. The Auk 80 (4): 504–539.
Bernard J.B. and Allen M.E. (1997). Feeding captive insectivorous animals: nutritional aspects of
insects as food. https://nagonline.net/wp-content/uploads/2014/01/NAG-FS003-97-Insects-
JONI-FEB-24-2002-MODIFIED.pdf.