The importance of green seed in the nitrogen nutrition of the Zebra Finch Taeniopygia guttata

Abstract

Australian grass-finches are widely reported to consume large quantities of green seed when it becomes available, and the opportunistic breeding of wild Zebra Finches in the arid zone has been correlated with the occurrence of rain. In this study, green and ripe seeds were harvested from seven pasture and weed grasses grown in experimental plots and, along with three cereal flours and whole-egg powder, were analysed for the amino-acid composition of their protein. The relative levels of ten amino acids essential in the diets of growing birds were compared between samples using a cluster analysis dendrogram generated from Raabe's Similarity Index. The protein of all green seeds clustered with whole egg, and away from all but one of the ripe seeds and seed products. Green and ripe seed profiles were found to be significantly different by a two-sample multivariate test of significance (Hotelling's T^). Histidine, lysine, phenylalanine and threonine were the amino acids most different. Of these four amino acids, lysine and threonine (along with methionine) were potentially limiting in ripe seeds when compared with whole-egg protein. In green seeds, lysine was only marginally limiting, threonine was no longer limiting, but methionine was still limiting when compared with whole-egg protein. These results indicate that the benefit of green vs ripe seed in the diet of breeding Zebra Finches is partly a higher level of the limiting essential amino acid, lysine, and partly a higher intake and throughput of sofr green seed and consequent greater extraction of limiting essential amino acids.

Does high growth rate of juvenile house mice with prolonged access to ripening grain and free water drive population outbreaks?

“…For example, the Australian zebra finch (Taeniopygia guttata) feeds almost exclusively on seeds, but breeds in the wild only in response to rainfall events that produce a sustained flush of ripening seed, irrespective of the availability of mature seed (Morton & Davies 1983;Zann et al 1995). Ripening seed provides the finches with a two-fold benefit: essential amino acids in higher and more balanced proportions than mature seed, and higher moisture content to aid digestive throughput (Allen & Hume 1997).…”

Changes in latitude, changes in attitude: a perspective on ecophysiological studies of Australian birds

“…More careful examination of free-living Zebra Finches, however, suggests that rainfall must be sufficient to stimulate germination of grass seed before these birds initiate breeding (Zann 1996). Interestingly, ripening green seeds have higher nutritional value and permit more rapid ingestion rates than fully ripe grass seeds (Allen and Hume 1997). Zebra Finches have also been presumed to be 'nonphotoperiodic' (e.g.…”

Low plasticity in digestive physiology constrains feeding ecology in diet specialist, zebra finch (Taeniopygia guttata)

“…Very narrow diet specialization, including relying only on seeds for feeding nestlings, is possible in granivorous birds when natural seeds have a relatively high protein content (Valera et al, 2005). In zebra finches, such a role can be played by the presence of green seeds following rain, which can provide breeding birds and nestlings with essential amino acids (Allen and Hume, 1997). Our results show that zebra finches have some extra capacity to increase protein intake, as they tolerated the diet with only 25% P. Brzęk and others starch and 46% protein well, which is presumably very different from the composition of their natural diet.…”