White-throated sparrow Study Reveals Four “Behavioral Sexes” in Nature

Recent research on the White-throated sparrow has highlighted how complex genetic systems in nature can shape a spectrum of social and reproductive roles, going beyond the traditional idea of just two sexes.

About the Bird

The white-throated sparrow is a small North American songbird identified by:

• Black-and-white or tan-and-brown striped head
• Bright yellow patch above each eye
• Distinct white throat patch

It breeds in forests of the northeastern United States and Canada and migrates to the southeastern U.S. during winter.

The “Four Sexes” Phenomenon

The species has two feather-pattern morphs—white-striped and tan-striped—present in both males and females.
This creates four behavioural sexes:

1. White-striped male
2. White-striped female
3. Tan-striped male
4. Tan-striped female

Each group shows different behaviour in aggression, singing frequency, and parental care.

Role of the Supergene

These morphs are linked to a special genetic structure called a supergene located on chromosome 2.
A supergene is a cluster of genes inherited together as a package, influencing multiple traits at once.

In this sparrow, the supergene:

• Emerged around 2 million years ago
• Controls feather pattern and behaviour
• Drives a rare disassortative mating system—white-striped birds usually pair with tan-striped birds

Unique Social System

• Birds are socially monogamous but often genetically polygamous
• Up to 40% of chicks in a nest may have different fathers
• Each morph contributes distinct parenting and territorial strategies

Source: TH