Tricky Coding Part I – Early Season Issues – when to code, and when to wait

By Tom Prestby May 3, 2016
American Redstart

In the first year of WBBA II, we all gained a lot of experience deciding what to code a given behavior and when to code it. The Atlas team just finished an extensive data review of the 2015 data (a huge thanks to Tom Prestby!) and it is clear that some judgement calls are harder to make than others. Everybody made mistakes in the first year, including the leaders of the project, so there’s no reason to feel bad if you did! This 4-part series titled “Tricky Coding” will address the most confusing situations from last year and serve as a study guide and reference for when these situations arise again. Being familiar with these articles will help everyone improve the quality of the Atlas data. We begin the series by addressing a timely issue since we’re in the middle of the passerine migration — when do you know it’s time to begin safely coding?

Be patient when birds return 

It’s easy to go right to that “S” code when you find your first singing sparrow, warbler, flycatcher, etc. after it returns from its wintering grounds far away. You may be familiar with the area and know that they typically stay throughout the summer. However, we urge you to be patient with assigning these possible codes. Good habitat for nesting birds is also good habitat for migrants so just because those orioles are singing on the edge of a lake in early May, while it’s likely they’ll stay, we can’t be sure yet. If you have the ability to check a location again after a species arrives, see if it’s still there next time. If it is, that’s a good sign that the bird plans to hang around. If you cannot get back to a site, especially if it’s in an area that is not likely to be covered by other birders, assess the behavior and habitat, and give a possible code if you think it’s on territory. If you aren’t sure, include some comments, even if they’re brief. 

Refer to breeding guideline bar chart 

The Breeding Guideline Bar Chart is your best friend for this tricky time of year when some species have reached their breeding grounds but others are still just moving through. This chart is a guide to determine if your bird is likely a breeder or if we are still in the migration window for some individuals. You can read a detailed article on the bar chart HERE, also another very useful tutorial for deciding when it is appropriate to give codes. We just completed a substantial revision of the bar chart, incorporating what we learned in 2015. If you’re wondering about a bird that is in the “B” category, it’s likely safe to code. If it’s in then “E” category, it could very well be OK to code but be careful because they’re still moving in parts of the state. If it’s in the M or N category, it’s best not to code lower codes because it probably has not entered its breeding cycle yet. However, always go with your observation over the chart, especially for early probable or confirmed codes. Remember, the chart is just a guideline. Exceptions do occur and the chart can’t possibly capture all the yearly and statewide variability in breeding timing!


Consult maps of known breeding ranges 

Knowing breeding ranges will further help you decide when to apply a code. Many species breed throughout the state but there are also quite a few that breed in limited regions. Birds that breed in the northern part of the state but commonly sing during migration in the southern part of the state, such as kinglets, vireos, and warblers, can be particularly deceiving. Some species like ducks even show courtship behavior during migration. Most range maps in field guides are accurate but we recommend using the maps from the first Atlas or the first year of the second Atlas to compare if you’re wondering about a species you don’t recognize as breeding locally.


Look for behavior 

A bird’s behavior gives good clues to help you decide if it’s likely on a breeding territory or not, early in the season. Singing is a clue that it might mean it plans to breed at the location, but this is far from a slam-dunk. Many birds will sing in migration, especially most passerines. The key is to assess how they’re singing. Using prominent perches and staying in a confined area (a possible territory) are good clues that it might stick around. Also, intensity and frequency of singing is a good clue. For example, if a bird is singing in the same spot a couple hours after you originally detect it, it may very well be on territory. However, be warned that migrants occasionally display this behavior too.

There are great several resources for bird behavior. The Birds of North America (BNA) is superior to all others but has a subscription fee. However, if you use the code “WBBA2”, you will get a year subscription for $25, almost half off the normal price! All About Birds is a good free website and some field guides also describe breeding vs. migratory behavior well. 

Beware of migrant traps — even when species is in range for geography and time 

The type of location you’re birding also can help solve if it’s a breeder or a migrant. If you’re at a migrant trap (along a great lake, at a park in an urban area, or at a park on an interior lake or river, be especially careful about coding. These locations are ideal for migrants and many birds do not stay and nest at these locations. Conversely, in the northern part of the state, many species arrive on their territories before they are detected anywhere else nearby so if habitat is ideal, codes can be applied if you’re in the correct timing window.


S for singing, H for non-singing 

The difference between the H and S codes is rather simple. If a male is singing on what seems like a territory, code “S”. If the bird is not singing or a female is singing but the habitat is ideal and timing is correct, code as “H”. CAUTION: There are several groups of birds that don’t make unique sounds to the breeding season so possible codes of these should always be coded “H”. A crow might be calling, but it’s calling the same way it calls in December, so that does not indicate breeding. Other species to be aware of include other ravens, jays, waxwings, hummingbirds, most waterfowl, and some woodpeckers. We will cover this issue in more detail in a later episode. 


S7 when present for a week in same area

One of the easiest ways to upgrade a species to Probable is to check back where it was singing at least a week later. If it is still in relatively the same location, congrats, you just upgraded it to probable! This code assumes you’re in the general area where you heard the bird last time, so it’s likely your original bird or a neighbor you’re hearing. So, this code should not be used for a bird heard singing a couple miles away from where one was heard on a previous visit. The assumption here is that the bird is holding a territory so only use “S7” if it seems that the bird is indeed holding a territory. This code also shouldn’t be used across years. The follow-up visit needs to occur during the same year because birds may arrive at different times in different years. It may seem weird that there isn’t a way to elevate those “H-only” birds (listed above) to probable based on repeated detections. That’s the case because repeated sightings have less value than repeated singing for breeding probability.

When in doubt, write comments in your checklist! 

Early season issues can be tricky. In the instances when you aren’t sure, leave a comment, which will aid in dealing with borderline situations later. Maybe the bar chart is wrong and we need to include your record. Maybe you’ve discovered a range extension we didn’t know about. PLEASE leave comments whenever you can — it can help when you and reviewers examine records later and we would hate for valid records to get weeded out during the eventual data review process. Something as little as one sentence can be extremely helpful.


In Conclusion 

You can see that there are several clues to look for when deciding if it’s time to code something. A combination of the above clues is best when applying a code, and when in doubt leave comments or seek help from one of the various venues or a birding friend. This is an exciting time of year because we’re detecting new species every day but just because they’re back doesn’t mean they’re breeding yet! Remember that the core of breeding season is in June and July for almost all Wisconsin species so being patient to code something until you’re sure is best, especially if you’re likely to return at a later time. If you choose to code something that you think may be borderline, remember comments, comments, comments!!

Happy spring migration and stay tuned for Part II!