How to identify the Merlin

To correctly identify the Merlin (Falco columbarius), check each of these features. Birds can be tricky: habit, habitat, and call often confirm a sighting that a single photo cannot.

Size at a glance

Length

24-33 cm (9.4-13 in)

Wingspan

53-73 cm (21-29 in)

Weight

Males: 120-210 g (4.2-7.4 oz); Females: 160-300 g (5.6-10.6 oz)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adult males (blue-backed Merlins) have a slate-blue to bluish-gray back and wings, often with faint black barring, and rufous-streaked underparts. Adult females and juveniles are browner overall, with dark brown backs and heavily streaked buffy underparts. All Merlins have a dark tail with narrow pale bands, and a faint malar stripe (mustache mark).

2. 2

   Beak shape

   Shape and color of the bill: a key field mark.

   Short, sharply hooked, dark gray to black with a yellow cere.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Dark brown

4. 4

   Leg color

   Leg and foot color.

   Yellow

5. 5

   Distinguishing features

   Standout features that separate this species.

   Small size, pointed wings, rapid wingbeats, and a distinctive flight style. Males are distinctly blue-backed. Females and juveniles are uniformly brown above. Faint malar stripe is present but not as prominent as in larger falcons. Tail has narrow pale bands.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Juveniles resemble adult females, being dark brown above with heavily streaked underparts. Their plumage is generally duller than adult females, and the streaking on the underparts can be bolder. The cere and legs are typically duller yellow than adults.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   No significant seasonal plumage changes beyond wear and tear. Plumage remains consistent between breeding and non-breeding seasons, though fresh plumage after molt may appear brighter.

8. 8

   Sexual dimorphism

   How males and females differ.

   Males are smaller and have a distinctive slate-blue back and wings, with rufous-streaked underparts. Females are larger and browner overall, with dark brown backs and heavily streaked underparts. This size difference is pronounced, with females being up to 25% larger and 50% heavier than males.

Key field marks

• Size and Shape. Small, compact falcon with pointed wings and a relatively short tail. Appears stockier than an American Kestrel.
• Flight Style. Fast, direct flight with rapid, shallow wingbeats. Often flies low to the ground. Agile and relentless in pursuit of prey.
• Plumage (Males). Slate-blue to bluish-gray back and wings, with rufous-streaked underparts. Faint malar stripe.
• Plumage (Females/Juveniles). Dark brown back and wings, with heavily streaked buffy underparts. Faint malar stripe. Juveniles are duller than adult females.
• Tail. Dark tail with narrow pale bands, visible from above and below.
• Head. Relatively small head for a raptor, with a faint malar stripe (mustache mark) that is less prominent than in other falcons.
• Vocalization. A rapid, high-pitched 'kik-kik-kik-kik' call, especially when agitated.

Explore the Merlin