Kestrels are small falcons found throughout much of the world. There are several different species of kestrel, but some of the more common ones include the American kestrel, Eurasian kestrel, and lesser kestrel. Kestrels are known for their ability to hover in place while hunting for prey. They primarily eat small mammals, birds, and insects.
When kestrels are young, they can be more difficult to identify to species as their plumage is drabber and they lack some of the distinct markings of adults. However, there are still ways to tell juvenile kestrels apart from adults and determine what species you are looking at.
Plumage Differences
The plumage or feather patterns of juvenile kestrels differ from adults in several key ways:
– Overall duller coloration – Young kestrels lack the colorful spotted patterns and sharply contrasting color patches of adults. Their feathers are darker, grayer, and less vibrant.
– Dark vertical streaking – Juveniles feature heavy vertical streaking on the breast, belly, and flanks. These dark markings provide camouflage for young birds.
– Grayish faces – The faces of juvenile kestrels are mostly gray rather than having the bright white or rufous faces of some adults.
– Barring on wings and tail – The flight feathers and tail feathers show dark barring bands rather than being plain.
– Spotting rather than striping on back – The backs of juveniles are lightly spotted rather than striped as in adults.
Behavioral Differences
In addition to plumage differences, juvenile kestrels behave differently than adult birds in some key ways:
– weaker flight skills – Young kestrels have less stamina and maneuverability in flight than adults. Their wings may appear a bit unsteady.
– More time spent perching – Juveniles will spend more time perched between short flights as their flight muscles are still developing.
– Short hunting forays – Immature kestrels make more frequent but shorter flights when hunting rather than hovering in place for long periods.
– Begging sounds – Young birds may retain some begging calls and sounds they used to solicit food from parents.
– Closer association with parents – Juveniles may still be loosely associated with, or trailing, their parents during the post-fledging period.
Size and Proportion Differences
There are some subtle differences in body size and proportions between juvenile and adult kestrels:
– Smaller overall size – Young kestrels are noticeably smaller in overall size though this difference decreases over time.
– Shorter tail – The tail of juveniles is shorter relative to the body than in adults.
– Large feet – Juveniles may appear large-footed as their body feathers are fluffy while feet have finished growing.
– Large heads – With fluffy body feathers, young kestrels can appear large-headed. The head looks proportionally bigger compared to the body.
– Thicker legs – The legs of juveniles are thicker relative to adults as immature birds have not fully slimmed down and shed all baby fat.
Distinguishing Different Species
While juvenile kestrels share many traits in common, there are some ways to identify which species you are looking at:
American Kestrel
– Dark tail with white tip (male) or dark band at tip (female)
– White or buffy vertical streaks on back rather than solid stripes
– Light facial streaking rather than solidly gray face
Eurasian Kestrel
– Black tip on tail (both sexes)
– Rufous tint to wings and back
– Dark ear patches
Lesser Kestrel
– Plain gray tail without any dark markings
– Entire back covered in fine dark streaking
– Pale grayish legs
Species | Juvenile Plumage Cues |
---|---|
American Kestrel | White streaked back, light face streaks |
Eurasian Kestrel | Rufous wings and back, dark ear patches |
Lesser Kestrel | Plain gray tail, streaked back, pale legs |
When do juvenile kestrels molt?
Juvenile kestrels generally hold their immature plumage through their first summer and fall. The molt into adult-like definitive plumage begins in their first spring. Here is a overview of the molting timeline:
Hatching to Fledging
– Nestling kestrels have downy gray feathers.
Fledging to Fall
– Fledglings and juveniles retain drabber plumage through first summer and fall.
First Spring
– Partial molt begins, replacing some body feathers.
Second Summer
– Near adult plumage but some juvenile wing coverts and tail feathers remain.
Second Fall
– Complete molt to definitive adult plumage.
So juveniles hold their distinct plumage for around a full year before molting. The molt is gradual over multiple seasons, not a sudden single molt. The complete adult plumage is not attained until around 15 months of age in most kestrels.
Why do juvenile and adult kestrels look different?
There are several reasons why juvenile kestrel plumage differs from the adult:
Camouflage – The drab patterns of streaking and spotting act as camouflage, helping to conceal vulnerable young kestrels in the nest and as fledglings.
Insulation – The fluffy juvenile plumage provides important insulation to help retain body heat. Young kestrels are more susceptible to cold.
Sun protection – Light feather patterning reflects sunlight and protects delicate young skin.
Developmental constraints – Juvenile feathers use simpler mechanisms and melanin pigments. The vivid melanins and structural colors of adults take time to develop.
Identification – Drabber plumages help birds identify conspecific juveniles and direct care and feeding appropriately rather than to other species.
So in summary, the differences help camouflage, protect, and identify juvenile kestrels during the crucial early stages of development. As they mature, adult plumage provides species recognition and sexual signaling.
What do juvenile kestrels eat?
The diet of a juvenile kestrel is quite similar to adult birds but adapted for their limited hunting skills:
– Small insects – Especially grasshoppers, crickets, beetles and caterpillars. Easy for young birds to capture.
– Small mammals – Voles, mice, shrews and young rats. Parents tear these into smaller pieces to feed young.
– Small birds – Nestlings and fledglings of songbirds, sparrows and finches. Easier for juveniles to catch.
– Reptiles and amphibians – Young lizards, tree frogs and snakes. More manageable than adults.
– Carrion – Juveniles will scavenge on carcasses of insects, birds and mammals. Important source of food.
– Bird eggs – Scrambled eggs of ground nesting birds. Offer high density nutrition.
The key is food that is soft, small, slow-moving or helpless enough for the developing hunting skills of juveniles. As they master flight and improve technique, their diet will expand to match the adults.
Do juvenile kestrels stay with their parents?
Juvenile kestrels have a somewhat prolonged association with parents after fledging:
– 0-2 weeks – Fledglings are dependent on parents for food as they learn to fly and hunt. Stick close to the nest.
– 2-4 weeks – Parents decrease feedings so juveniles start hunting on their own. Stay loosely near parents.
– 1-2 months – Juveniles become independent but may remain in the area and occasionally associate, interact or roost with parents.
– Fall migration – The association breaks off completely as adults and juveniles migrate separately.
Though independent after 8 weeks or so, the post-fledging period helps juveniles refine skills and learn while benefiting from some degree of protection thanks to the parents nearby. This increases survival during the crucial early part of life.
Conclusion
Identifying juvenile kestrels and distinguishing them from adults does take some practice. But paying attention to key differences in plumage patterns, proportions, behavior, and vocalizations allows a positive identification. Appreciating why juveniles look and act differently – for camouflage, insulation, energy efficiency and identification – helps narrow down what species you are observing. With a little time observing kestrels through the seasons, both the juvenile and stunning adult plumages become easier to recognize in the field.