When Fledglings Become Juveniles

ArrayAugust 15, 2018 at 1:10 pm

[caption id="attachment_769" align="aligncenter" width="640"] Black-capped Chickadee Poecile atricapillus Doug Hitchcox[/caption] July is a great month for atlasing Adults can easily be seen carrying food, baby birds are chasing their parents around begging for meals, there are even some birds working on a second (or third) brood already. As some of our early nesting species mature, it is worth taking a moment to review what birds should be coded in the atlas, and at what stage in their development we need to be more cautious. Simply put:Be careful to not code juvenile birds wandering outside of the block where they originated. Our goal for this atlas is to know which species are breeding in each block in Maine, so as baby birds grow and develop they will age-out of any breeding codes that we can use for the atlas. These juvenile birds can still be entered on your eBird checklist (you can include a note to remind yourself to look for them nesting in future years) but no codes should be applied. Here are some things to look for in the questionable birds: Retaining downy plumage Fresh out of the egg, most birds are going to grow a set of downy feathers before their juvenile plumage comes in. Recently fledged birds are likely to still show a few of those downy feathers sticking out among the juvenile. Tail-length Among those juvenile feathers, the tail is generally the last group to fully grow in. Recently fledged birds will often show shorter tails than their adults. Use caution with adults that may be showing molt limits as they replace tail feathers in the fall. Combining this with traits like a visible gape-line are helpful in aging these birds. Foraging on its own Recently fledged birds will usually be fed by their adults for several days after leaving their nest. Within this time it is unlikely they are traveling very far from their nest so we can assume that if they are still foraging with their adults then they are probably within the block the nested in. Strong flight This could be combined with some of the earlier criteria but generally recently fledged birds will be weak fliers, only traveling short distances and often not efficient at grabbing perches. Young birds that are seen flying around with adults While all of these traits are helpful, it is probably best to look for multiple of them and not rely on single features. To further illustrate this, here are a few more specific examples: Canada Goose (and other waterfowl) Any downy, yellow-plumaged chicks should be entered as FL Recently Fledged Young but once they are getting larger and looking like small, runty versions of the adults, they should not be coded. Glossy Ibis (and other herons/egrets) Young birds are dispersing from the rookeries they were born in, so birds that appear recently fledged are showing up miles from their nests and should not be coded. Terns Fledgling terns are leaving the islands that they were born on and can often be seen being fed along the coast. While these birds are still dependent on their adults we DO NOT want to code this behavior because those birds are being seen away from their nesting site and likely outside of the block their nest was in. Shorebirds Fall migration has begun so do not code any flying juveniles. Downy chicks that are still flightless (Killdeer are still raising young and there are a few Piping Plover chicks on beaches) can be coded FL but avoid coding older birds capable of flight. Feeder birds Use cation with juvenile birds at feeders. Behaviors like the adults feeding young at feeders can still use the code FY Feeding Young, and family groups that are likely to have nested locally can use FL Recently Fledged Young. We are already seeing juvenile birds dispersing so be careful with species like Common Grackles or Purple Finches that may be far from the blocks they nested in. Corvids Immature crows and ravens are following their parents all over. Again, use caution with juvenile birds that may be traveling far distances.