# Molecular Determination of Sex from Down and Feather in Wild and Reared Monomorphic and Dimorphic Birds at Juvenile Age

## TL;DR

This paper shows how DNA from down and feathers can be used to determine the sex of young birds, helping in breeding and conservation efforts.

## Contribution

The study demonstrates a non-invasive method for early sex determination in birds using DNA from feathers and down.

## Key findings

- DNA from down and feathers is a suitable and non-invasive source for sex determination in young birds.
- The method successfully identified the sex of 153 avian species, including 27 for the first time.
- All tested pairs produced offspring, confirming the accuracy of the sexing method.

## Abstract

Interest in the breeding of feathered species has grown increasingly in recent years to the extent that early sexing has become necessary to ensure the formation of the pairs that will guarantee the birth of new birds. When sex identification must be carried out in very young individuals, sex is hardly recognizable not only in monomorphic species but also in dimorphic ones. The employment of molecular techniques is particularly necessary when the assessment of biometric parameters does not allow a clear sex identification. Recovery of DNA is mandatory when molecular techniques are used. In this paper, we demonstrate that down and feathers are suitable sources for DNA recovery without causing severe stress to the bird. This is a crucial aspect when dealing with nestlings. Using this procedure, we identified the gender of 153 avian species, including 27 for the first time.

The inability to distinguish males from females in young birds is a major obstacle for pair formation in reintroduction–restocking programs and commercial–amateur breeding. Several techniques are employed to address this problem, but not all of them are suitable for juvenile subjects. Among the various tests applied for sex determination, polymerase chain reaction (PCR) is one of the genetic tools that seems to be most effective (rapid, not invasive and cheaper). In this study, DNA was extracted from down and feathers to make the procedure less stressful for nestlings. The DNA was amplified by PCR, and the amplicon was subjected to the restriction endonucleases procedure when the gender was not clearly identified by PCR alone. One hundred and fifty-three avian species were sexed using this procedure, including 27 for the first time. In all the nestlings and juveniles tested, sex was correctly identified; in fact, all pairs that reached sexual maturity during this study gave offspring.