Tricky Codes IV: Atlasing season is almost over, but not yet!

By Tom Prestby August 11, 2016

Now that we’re well into summer, the atlasing is slower and the heat and humidity is often nearly unbearable. If you’re thinking the atlasing season is winding down, you’re correct. However, it is not over yet! There is still plenty of activity and atlas codes to be found, especially confirmations. Although it’s not as easy to assume breeding as it has been for the past couple months, atlasers will still be rewarded with confirmations for the next couple weeks. Read on to learn what situations you can still confidently confirm breeding, when it’s likely too late, which codes to use, and some other tips for atlasing during this tricky end of the season period.

I see a juvenile, how do I know if it was hatched in the block? 

Finding juvenile birds is rather easy right now compared to other parts of summer. Many songbirds have distinct field marks (often extra streaking, buffiness, a pale gape, or different eye color) that identify them as a juvenile. Many times they’ll look different proportionally as well, with shorter tail or wings than adults of the same species. Sometimes you can also still see down on a bird, especially on the head– another good clue that it was hatched this year. Once juveniles have outgrown their fledgling raggedy appearance, they’ll often look very fresh compared to faded or raggedy late-summer molting adults. Beware that adults are often molting and rather raggedy right now so the bird may look undeveloped like a fledgling, but it’s actually an adult. You can learn more about juvenile bird ID in your field guide of choice or see Tom Schultz’s excellent presentation on the topic from this year’s atlas kickoff meeting.

So, once you’ve found a juvenile, the question is how do you code it? A clear black and white answer is rare but we can look for clues that point one way or the other. Using the clues below as guidelines, you’ll have a good idea if your observation should be coded or not, especially if you witness a combination of clues pointing one way or the other.


Likely was hatched in the block, often warrants FL code: 

  • The species was steadily present at or near the location this summer
  • The bird is closely associating with more of the same species, likely siblings or parents
    • Seeing more than 2 of the same species together (other than those which typically flock like chickadees or corvids) is a good sign!
  • The species tends to not move in mixed flocks before it migrates
  • The bird is still giving unfamiliar call notes which could be begging calls
    • If you have spent a lot of time in the field, you’ll likely know a call is different
  • It’s a species that often flocks but has not done so yet
    • e.g.: Warblers or sparrows
  • The bird is still noticeably undeveloped in growth
    • Reminder, beware of molting adults that may initially look like fledglings

Likely was not hatched in your block, doesn’t warrant any code: 

  • This is the first time you’ve detected the species in the area this summer
    • A red flag if you’ve been thoroughly covering a block!
  • The habitat might be OK but does not seem ideal
    • Another red flag, a big red flag in combination with above, although this can be tricky because in some cases birds will move to an adjacent habitat that provides better foraging or cover for young, especially shrubby forest edges.
  • The bird is in a mixed flock with several more juveniles but few adults
    • This could indicate the birds are too old to code and may have dispersed from their original territory
  • There is no sign of adults that it is following or associating with
  • The species is known to disperse after breeding
    • Common with waterbirds. Night-herons, gulls, terns, birds of prey are examples
  • The bird is a little south of its normal breeding range
    • Could easily already be migrating
  • It’s alone, fully developed, and flying well
    • e.g.: flycatchers, tanagers, that aren’t with parents

Code refresher: FL vs FY vs CF 

These are the most common confirmation codes to be used in late summer. Since they’re all confirmations, don’t worry too much about situations where you could use either code, but it shouldn’t be too difficult to decide which code to use. Rules of thumb:

  • CF: You saw an adult with food in its bill but could not follow it to its destination
    • Do not use the code for a split-second look or if it ends up swallowing the food
    • Do not use with terns or gulls and be very careful with corvids and birds of prey


  • FY: You saw an adult feed one or more juveniles out of the nest
    • Can also be used if you see CF and the bird disappears behind some vegetation but begging calls are heard since this is assumed
    • Terns will do this away from breeding sites so use extreme caution


  • FL: You saw presumed local juveniles but you never saw them get fed by an adult
    • Even if they are obviously following adults around
    • e.g.: Duck/game bird broods are FL unless you see the adult feeding the young
    • Reminder to be cautious in evaluation and consider the clues above

Grebe Pied-billed

Late-season use of other codes 

As long as you believe the bird is still on territory, feel free to keep using other codes that you observe, as some are surely still occurring. Even if you have already confirmed a species for a block, in general we encourage you to code whatever behavior you witness (including the general H code for present in appropriate habitat). However, as we get into August, H and S codes become a less safe assumption, particularly in locations you have not been visiting all summer (and even P, M, and S7 codes become less reliable). Entering codes whenever you see them will result in a better understanding of how long birds use their breeding territories and how they are being used. However, we realize this may be tedious so if you do not have the time to enter lower codes for post-confirmed species, it’s OK. Always focus on upgrading codes, especially seeking confirmations this time of year, instead of tracking behavior of species that are already confirmed.


Still don’t know? Don’t worry! Ask for help and use comments 

Sometimes even with all the possible guidelines, it’s still a really tough call whether a young bird is local or not. This is common, even for the most experienced atlasers so don’t feel frustrated or ashamed. The Wisconsin Breeding Bird Atlas Photos and Discussion Facebook group is a perfect venue for these questions and they provide great challenges in which everyone learns. You can also send a question to the Atlas Forum, your county coordinator, or any atlasing friend. There is more detailed info on late-season issues from another atlas eBird story as well. At the very least, include a photo and/or some comments about the plumage and situation so you and the reviewers have more information to work with when these difficult records are evaluated.

Tips for late-season atlasing 

  • These are the dog days of summer—atlas in the morning or evening to avoid the hottest part of the day not only for your health but because most birds are much less active and harder to find when it’s hot and sunny.
  • Cloudy and cooler days are often much more productive, especially after early morning. If you can get out immediately after a morning rain, atlasing can be phenomenal.
  • During cool mornings, work open areas and edges that the sun is hitting. Once it heats up, work the cooler and shaded forested areas.
  • Listen for and track down chip notes! These often lead to confirmations this time of year.
  • There will be long stretches of no activity. Don’t lose courage, keep covering ground. You will often find birds (and confirmations) in waves and some waves can still be extremely productive, even if few and far between.
  • Remember, even if they are all full-sized, if you see several members of a species (with some exceptions) happily associating, you’re likely seeing a family. Close examination may reveal some of these are juveniles. However, as August wears on, beware of migrant flocks. Consider the species — 5 White-throated Sparrows could be a migrant flock if you cannot identify any juvenile characteristics, but 5 American Kestrels sitting on the same wire will never be migrant adults, and must be a family group.
  • Remember to scrutinize juveniles that show any of the signs of not being hatched locally.
  • Some late-breeding species like goldfinches and waxwings are just now into the peak of their breeding seasons. Now is the time to confirm these stragglers!
  • Other species often have multiple broods, including common species like American Robin, Mourning Dove, Red-winged Blackbird, Eastern Bluebird, and wrens. They might still be tending to small young. Also, any species might have tried renesting if they lost their first nest.
  • Consult our Breeding Chronology Chart from the 2015 season to help figure out which species are prone to being confirmed in the later months.
  • Worried that your block has less confirmations and detections than it should? That’s OK, there’s 3 more years left! We encourage you to hit your block again if you think it will be productive but don’t sink a lot of hours into these late-season visits.


Thank you for another very successful atlas season and take advantage of these last couple weeks, let’s finish off 2016 strong!


Photos copyright Tom Prestby (Pied-billed Grebe, Cooper’s Hawk, Brewer’s Blackbird), Tom Schultz (Eastern Towhee), Ryan Brady (Nashville Warbler), Nick Anich (American Robin).