1. Siskins: Siskins, such as the Pine Siskin and the Common Siskin, are closely related to goldfinches and share similar physical characteristics and behaviors. They have a similar body size, wing shape, and feeding habits.
2. Redpolls: Redpolls are another group of birds that are closely related to goldfinches. They are small, active birds with bright red caps on their heads. Common species include the Common Redpoll and the Hornemann's Redpoll.
3. Crossbills: Crossbills are unique among finches due to their crossed mandibles, which they use to extract seeds from conifer cones. They are related to goldfinches and share some similarities in their plumage and behavior.
4. Chaffinches: Chaffinches are European finches that are closely related to goldfinches. They are slightly larger than goldfinches and have distinctive black-and-white markings on their heads and wings.
5. Bullfinches: Bullfinches are another group of finches that are related to goldfinches. They are stockier than goldfinches and have a distinctive red breast and black cap.
These birds share similar ecological roles and often occupy similar habitats, competing for food and nesting sites. They may also engage in hybridization, resulting in the formation of hybrid species.