Minimum slope to prevent birds nesting 1

[bugbus]

A bit of an unusual one...

Does anyone have experience in designing exposed ledges etc. with a deliberate slope to prevent birds from taking up residence?

This recently came up on a new bridge design, with large concrete I girders. The bottom flange originally had a horizonal top surface, but we decided to put a 1:5 slope on it to assist with drainage and to discourage birds from nesting. This was mostly a stab in the dark.

Since then, I have read this:

"The maximum outlet width a pigeon is not able to pass through is 4 cm; the respective outlet height is 5 cm and a pigeon-safe square opening is not larger than 6×6 cm. The maximum ledge width a pigeon is not able to sit on is 4 cm. The pigeon-safe angle of inclination for smooth construction materials (tinplate, glass, plastics) is 25°, for medium rough materials (wood, plane concrete) 35°, and for rough materials (sandstone, rough concrete) at least 50°."

Link to paper:

https://core.ac.uk/download/pdf/159152875.pdf

This seems a little steep to me. Have never seen a bird nesting on a 45 degree slope before.

Anyone have any more thoughts or experience?

 

[MIStructE_IRE]

Unless the bird reads the code of practice then your guess is as good as mine!

Usually we just see the little plastic spikes being put in to stop them nesting/chilling out.

 

[BridgeSmith]

We have Mud Daubers that build their nests under the top flanges of steel girders. I had one bridge where the local 'wildlife enthusiasts' were thrilled I made the bottom flanges wide enough for birds to nest on.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[3DDave]

Birds nested on top of the 4 inch diameter ABS exhaust vent for my furnace on top of the final elbow before it goes horizontal. It is slick, sharply curved, not well protected from weather, roars when the heat comes on in the Spring during the building of the nest, and very steep. Robins set up shop there.

The best way to prevent nesting is to provide easy access to ground-based predators. If it looks like a cat can reach the location easily the birds are likely to find somewhere else. Or a cat will be fed.

You can provide a candidate site in compensation that is in a predator deterrent location, or try the anti-bird spikes.

 

[rb1957]

"ground-based predators" ... damnn, I like the way you think !

another day in paradise, or is paradise one day closer ?