Savannah Sparrow

The Savannah Sparrow is one of the most numerous songbirds in North America with a loud, insect-like sounding song, which can be heard in farm fields and grasslands. It breeds throughout Canada and the northern US, and, is a year-round resident in southern coastal and Baja California and Central Mexico. It winters in the southern US, Mexico and northern Central America.

Adult Male (spring/summer)

Head has whitish median crown stripe, brown lateral crown stripe, yellowish supraloral, complete strong eyeline and moustachial stripe, and buffy brown auriculars. Bill is small and pink and head sometimes gives crested appearance. Chin white, breast and flanks white with crisp dark streaks. Belly and undertail coverts white. Nape, back, rump and uppertail coverts brown with streaks without scaly pattern. Wings and short-notched tail brown with streaks. Legs pink with long toes.

Adult Female (spring/summer)

Similar to adult male.

Juvenile

Similar to adult, but buffier. Median crown stripe less distinct and supraloral duller yellow.

General:

Medium size sparrow with short, notched tail. Length: 11-15cm. Wing: 20-22cm. Weight: 15-28grams.

Behaviour:

The Savannah Sparrow walks along the ground to forage for bugs occasionally running or hopping to seize prey. Flights are typically low and quick among grasses. They have a bounding, buoyant flight unlike other grassland birds. They are inconspicuous birds but males are conspicuous during breeding season singing from perches like tops of shrubs, grasses and fence posts. Their diet consists mainly of insects during breeding season and seeds during winter.

Habitat:

Common and widespread in open grassy or weedy habitats, including marshes, fields and dunes, less numerous in brushy habitats. Often form loose flocks in winter.

Information:

In many parts of the species’ range, especially in coastal areas and islands, Savannah Sparrows tend very strongly to return each year to the area where they hatched. This tendency, called natal philopatry, is the driving force for differentiation of numerous Savannah Sparrow subspecies. The nest is low to the ground in thick thatches of prior seasons dead grasses. It is a cup within a cup. The outside cup is comprised of coarse grasses with a finely woven inner cup of thin grasses. Clutch is 2-6 pale greenish, bluish, tan or white with speckles and streaked eggs.

Similar species:

Conservation Status:

Listed as Least Concern.

Capture Rates:

The open habitat of Colony Farm provides breeding habitat for the Savannah Sparrow. Capture rates begin as individuals arrive from their wintering grounds. Numbers peak in September as young disperse and prepare to return to their wintering areas in the southern USA and Central America.

Molt Summary:

PF: HY partial; PB: AHY complete; PA limited-incomplete
Preformative molt usually includes all med and gr covs and usually 1 – 3 terts but no rects
The Pacific Coastal subspecies average slightly more feathers replaced at the preformative than other subspecies
PA includes no gr covs, sometimes 1 – 3 terts, and sometimes 1 – 2 central rects (r1; rarely up to 4 rects)
1st and adult PA are similar in extent.

Note: Beware of colour contrasts (or pseudolimits) between the secondaries and tertials in adult (AHY/ASY) birds. Examine the extent of wear to the feather tips to see if it is a true molt limit.

This HY in September is in the midst of its partial preformative molt with greater coverts in sheath – a molt limit in the making between the outermost greater covert (GC1) in sheath (red arrow) and innermost primary covert.

The sequence of events in a partial preformative molt can be seen here as this bird replaces lesser, median and greater coverts, but not the lower two main alula feathers, carpal covert, primaries, secondaries or primary coverts which are all retained juvenal feathers.

Notice the washed out appearance and narrow and tapered main alula feathers and outer primary coverts.

This HY also in September has completed its partial preformative molt and replaced lesser, median and greater coverts and innermost tertials (S8 & S9), the molt limits indicated with red arrows.

Again, notice the washed out appearance and narrow and tapered main alula feathers and outer primary coverts.

Savannah Sparrows are among the Emberizid family which often show a key alula covert (A1) molt limit where the greater alula covert, as part of the median tract of feathers, is replaced showing a contrast between it and the lower main alula feathers. That is not the case with this individual which has retained the greater alula covert.

This HY also in September has completed its partial preformative molt and replaced lesser, median and greater coverts and innermost tertials (S8 & S9), the molt limits indicated with red arrows.

Again, notice the washed out appearance and narrow and tapered lower main alula feathers and outer primary coverts.

This individual is showing the key greater alula covert (A1) molt limit mentioned above (small red arrow). Notice the contrast between it and the more lightly pigmented lower main alula feathers.

Tail shape is helpful in ageing many species being tapered and more abraded on retained juvenal feathers in first year birds (HY/SY) and broad and truncate with a corner to the inner web and relatively fresh in adults (AHY/ASY). The outer retrices (R4-R6) tend to show the greatest age specific differences.

The very fact that tail feathers are frequently lost and replaced between normal molts is one of the reasons why tail feather shape must be used with great caution by banders, and only with other supporting characters (e.g., molt limits), when determining the ages of birds in hand.

This HY in September is showing very tapered outer rectrices diagnostic of first year birds.

This AHY in April is a good example how not every bird can be accurately aged SY/ASY in the spring and care should be taken especially with birds that live in environments where plumage is more prone to wear.

Savannah Sparrows are one such example, typically found in grasslands , meadows and cultivated fields and where on the breeding grounds males sing persistently from exposed perches where plumage is exposed to radiation and the elements.

This bird has very obviously replaced the two inner tertials (red arrow) as part of its prealternate molt in the spring but even under maximum magnification it is difficult to determine if there is a molt limit between replaced greater coverts and primary coverts as the wear to the tips of all of these feathers looks identical. There is a very faint contrast between the greater alula covert and lower alula feathers and the outer primary coverts look narrow, tapered and abraded but the remiges look truncate with little wear (other than S7).

The tail of the same bird is equally inconclusive with central rectrices (R1-R2) replaced in the prealternate molt but outer rectrices somewhat tapered and relatively abraded.

Although a helpful clue to ageing birds in the hand, tail shape should always be used with caution and never alone as it is generally not very reliable because of a) individual variation and b) the possibility of accidental loss and replacement (called adventitious molt).

This ASY in April showing only two generations of feathers (i.e. adult basic and adult alternate), the bird having replaced all body and flight feathers in its definitive adult prebasic molt following the breeding season last year and innermost tertials (S8 & S9) shown with red arrows in its adult prealternate molt in the late winter / early spring.
Notice the consistency between the feather groups, the uniformly adult primaries and secondaries with very little wear and dark, glossy alula feathers and primary coverts and compare to the AHY and HY birds above.