Migration Research Foundation - McGill Bird Observatory - Photo Library

McGILL BIRD OBSERVATORY

PHOTO LIBRARY

Tree Swallow / Hirondelle bicolore (Tachycineta bicolor)

Seasonal status at MBO:

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

common

fairly common

uncommon

rare

occasional

no records

QUICK TIPS: (applicable only in spring/summer)

1) Consider the body plumage:
     - if there is any brown on the head or back in spring/summer the bird is a female
          - >50% brown indicates a SY female
          - 10-50% brown indicates an AHY female (zone of overlap in plumage between SY and ASY)
          - 1-10% brown indicates an ASY female
     - if the head and back are entirely green-blue it may be a male of any age or an ASY female

2) Check the flattened wing chord - if it is <114 mm the bird is a female, if it is >121 mm the bird is a male

Note: the above tips are based on the long-term research of Dr. David Hussell at Long Point Bird Observatory

Species account updated April 2009

Ageing and sexing overview:

January - July:

AHY - M Upperparts entirely blue-green; sex must be confirmed by cloacal protuberance.
ASY - F Upperparts almost completely to entirely blue-green; sex must be confirmed by brood patch.
AHY - F Upperparts 50-90% blue-green.
SY - F Upperparts over 50% brown.

June - December:

AHY - M
AHY - F
HY - M
HY - F
JUV - U

Ageing and sexing details:

after-hatch-year male

In spring, male Tree Swallows of all ages are entirely blue-green above. Unless there is abnormal retention of brown juvenile feathers, age cannot be determined. Some males can be sexed if they have a sufficiently long flattened wing chord (at least 121 mm). Otherwise, sex can be reliably assessed only through the presence of a cloacal protuberance, as ASY females can also be entirely blue-green above.

Photo by Marcel Gahbauer, April 2006

Wings are uniform in colour, with a blue-green sheen to the coverts and tertials.

Photo by Marcel Gahbauer, May 2006

The blue-green upperparts extend through to the rump, and there is often a blue-green tinge to the rectrices.

Photo by Marcel Gahbauer, May 2006

RETURN TO AGE/SEX OVERVIEW

after-second-year female

In spring, ASY female Tree Swallows are 90-99% blue-green on their upperparts, and can be virtually indistinguishable from males. Some females can be sexed reliably by wing chord, if it is 114 mm or shorter. Otherwise, any Tree Swallows with this colouration must be sexed as females only if they have a brood patch.

Photo by Marcel Gahbauer, April 2006

Wings are uniform in colour, with a blue-green sheen to the coverts and tertials.

Photo by Marie-Anne Hudson, May 2008

The blue-green upperparts extend through to the rump, and there is often a blue-green tinge to the rectrices.

Photo by Marie-Anne Hudson, May 2008

RETURN TO AGE/SEX OVERVIEW

after-hatch-year female

Some female Tree Swallows have more (>50%) blue-green on the upperparts than is typical of SY birds, and less (<90%) than definite ASY females. They can be recognized as females by having at least 10% brown feathers, especially on the forehead, and sex can be confirmed by brood patch, but age cannot be determined with accuracy.

Photo by Marcel Gahbauer, April 2006

Wings may have a blue-green sheen in places, or may be largely brown.

Photo by Marcel Gahbauer, April 2006

The blue-green upperparts eusually xtend through to the rump, and there is often a blue-green tinge to the rectrices.

Photo by Marcel Gahbauer, April 2006

RETURN TO AGE/SEX OVERVIEW

second-year female

Primarily brown above, with dull blue-green flecks covering up to 50% of the upperparts; the amount of blue-green on the head may be quite variable, as shown by the photos below.

Photo by Marcel Gahbauer, June 2006

Photo by Marcel Gahbauer, April 2006

Photo by Marie-Anne Hudson, May 2007

The wing is mostly brown, though on some individuals there may be some feathers, especially toward the back, that have a fair amount of blue-green gloss.

Photo by Marcel Gahbauer, June 2006