Definition of "siskin"

I sat there on a bench in dappled shade, beside an aviary full of brightly feathered finches and siskins fluttering about.

2001, WG Sebald, translated by Anthea Bell, Austerlitz, Penguin, published 2011, page 2

Many of these classic methods are still used, with some modern improvements. For example, with the aid of special microphones and automated sound detection software, ornithologists recently reported […] that pine siskins (Spinus pinus) undergo an irregular, nomadic type of nocturnal migration.

2013 January, Paul Bartell, Ashli Moore, “Avian Migration: The Ultimate Red-Eye Flight”, in American Scientist‎, volume 101, number 1, archived from the original on 5 March 2016, pages 47–48