Bird-X model. Then, upon its disappearance from the shelves, we started hand making and selling our own. Theirs or ours, House Sparrows (HOSP) were 100% eliminated -- not just from our feeders (2, pure black oil sunflower and safflower), but from the entire gardens it seemed.
After 4 HOSP-free years, for the first time, we decided to keep the feeders going year-round (2020), to ensure Halo efficacy remained consistent during the hot weather months. As it turned out, this was not the case; at some point during mid-Summer, a single HOSP would appear at a time. Then one became two, and then a few at a time as we entered late Summer and Fall. Now as many as 3-5 HOSP can be seen at a time making it through the hanging wires, but their behavior at the feeder is usually nervous and erratic, and they usually don't stay long (some longer than others).
So, in order to test efficacy, we did a few experiments. We found that removing the Halo does bring about a surge in HOSP numbers, and makes them more comfortable and thus more aggressive at the feeders. Therefore, at least in our observation, keeping the Halo up still serves as a deterrent and helps reduce seed consumption -- and thus cuts refill rates and costs. If this wasn't the case, we would have to consider ending Magic Halo production and quit selling the device. We hope it never comes to that.
So the question becomes, how did this happen, after years of 100% HOSP-free feeding? It is impossible to know without a university taking up the cause with scientific studies. But the most plausible theory has to do with leaving the feeders up through Summer (year-round). It would seem likely that HOSP juveniles nesting nearby (20 chicks avg per year per pair) commandeered our gardens in Spring, making it their territory and regular source of food. As first year birds, they started out immune to lines (wires), as shown in the original U of Neb studies. As the season went on, continued adaptation followed. Given this observation, we had to update our disclaimer to further emphasize the issue of juveniles and that Halos are best viewed as an adult HOSP deterrent, not "-proof" though many folks continue with feedback that it is (and it was for us, until this year).
We hope this helps our customers understand, and to continue using their Magic Halo as just one tool in the toolbox in the effort to reduce or eliminate HOSP from their feeders. Each year, we offer a new survey in order to keep efficacy data rolling in, so please participate as much as you can. Our surveys do not require any personal info and are 100% safe and secure. If you haven't already, please take the 2021 Survey. Written feedback (firstname.lastname@example.org) with attached photos of your feeding setup is also very much appreciated, and will be considered for this blog. As always, let us know your experiences using the Magic Halo!