The Yellow Warbler (aestiva group; 6 subspecies4 breeds in the whole of temperate North America as far south as central Mexico in open, often wet, woods or shrub. It is migratory, wintering in Central and South America. They are very rare vagrants to western Europe.3
Depending on subspecies, it may be between 10–18 cm (3.9–7.1 in) long, with an average wingspan of about 20 cm (7.9 in). They weigh 7–25 g (0.25–0.88 oz), varying between subspecies and whether on migration or not, globally averaging about 16 g (0.56 oz) but only 9–10 g (0.32–0.35 oz) in most breeding adults of the United States populations. The summer males of this group are generally the yellowest “warblers” wherever they occur. They are brilliant yellow below and golden-green above. There are usually a few wide washed-out rusty-red streaks on the breast and flanks. The various subspecies in this group mostly in brightness and size as per Bergmann’s and Gloger’s Rule.7.
Image taken in Lyndhurst, Ontario with the Canon 50D and 100-400 lens.