In response to the recent attention on Jerseybirds, I figured I’d post a quick note.
You can read the original posts here:
To clarify, with some time and effort, radar data can be analyzed to estimate absolute numbers of birds migrating overhead. These values are highly variable under certain weather conditions, and therefore most studies that use such data choose them subjectively to minimize contamination by precipitation, insects, etc. Furthermore, radar data “out of the box” needs to be post processed to correct for certain inherent qualities which bias the data. This is NOT what I do on woodcreeper.com (but it IS what I do for NJ Audubon). Most of what I do on woodcreeper.com is off-the-cuff analyses of the weather forecast, backed up (or not) by the nightly radar, and my (limited but growing) understanding of bird migration over New Jersey (and to a lesser extent, elsewhere). Trying to estimate bird density (on a very non-quantitative scale of “low” to “high” and sometimes “really fricking crazy”) every night has an inherent level of inaccuracy (sometimes very high!). Couple that with the fact that birds overhead does NOT mean birds on the ground the following morning, and you begin to understand that predicting birding conditions based on weather and radar is both an art AND a science (with art trumping science under conditions where the predictive properties of weather or radar decline). My post yesterday was tongue-in-cheek towards Mike Hiotis, but in total seriousness, what I do on a daily basis is meant to better understand what factors are driving birds into the places we find them (and don’t find them). So any observations to that end are productive towards our general understanding of the relationships between weather, what we see on the radar, and birds on the ground.
If I “say” that there are no birds migrating, it’s almost always based on the radar (read: the radar detected no birds migrating). West winds last night could easily have brought an influx of birds from PA, but they weren’t showing up on the radar last night- so the only way to know would have been to a) listen during the night for flight calls and/or b) get out and bird. Walt should not feel compelled to qualify his report- he went birding, there were new birds = some birds migrated* (*assuming he or someone else was there yesterday, and counted less birds). That’s interesting! and also gives us one more data point where the radar just couldn’t pick it up.