Windex now makes their spar fly products (10 and 15") with a spike that sticks into the air above the vane to keep the birds from perching.
You're mixing up 2 different DAVIS products. The model with that spike is the WINDEX 15, not sure if they have now added the spike to the larger (Big Boat) model and the smaller (WINDEX 10) model. The SPAR-FLY is a less expensive wind-vane and is what I have on my O'DAY Day Sailer II. It works pretty good, doesn't have the "tacking arms" of the WINDEX, nor is it as rubust looking as the more expensive and technically advanced WINDEX models..... but it works for me.
However, one reason that I stick with the Spar-Fly is that I too have trouble with birds landing on my wind-vane, or at least I assume that is what keeps breaking it. We have cormorants in our area and they love to land on mast heads (and surprisingly, round spreaders!) I don't think they could land on my Spar-Fly, but it is either that or the local pair of Ospreys. At least a replacement vane for the Spar-Fly is only around $8, but my mast is not deck-stepped.... so, replacing the vane is not an easy task in mid-season! I need to find a friend with a much larger sailboat......and a bosun's chair, either that or someone with a larger trawler (or tuna tower?). Who said powerboats are worthless??
I used to have a Spar-Fly on my old O'DAY Widgeon, had the same problem with birds. However, on a smal lboat like that.... I could just bring her into shore and pull her up on edge of the marsh at high-tide, reach up and grab the mast, step in the gunwale and roll her over enough to reach the mast head. Then it was easy to replace the broken vane. Not so easy on my DS II.
Now, for a quick bit of extra praise for DAVIS INSTRUMENTS, twice after having birds break the vane on my Spar-Fly (on the Widgeon), I happened to speak to them at the Newport, RI Boat show. To their credit, on both occasions... I was handed a form to fill out (about 1/2 page) and about a week or less later a brand new replacement vane appeared in my mailbox, NO CHARGE!! That is the other reason why I remain a loyal customer of their products.
Still, I'm a bit timid about upgrading to a WINDEX..........unless I can be 100% sure it won't be broken by a bird! Maybe that spike is the answer?