I must say, I have never had any problems with sparrows. My only concern with having dowelled fronts to any loft is giving access to rats. Personally I haven't had a problem with rats, as the loft is 18 inches above ground and my dog often scurries under the loft and I never leave food in the loft. However, at night, when all the birds have retired to their perches, I close the loft up, so they don't have access to the aviary and have a wireless alarm sensor in the corridor, which alerts me in side the house if there is an intrusion, human or vermin. But it's a valid point and one I did consider, especially at £1.25 per 6 ft dowel. If cosmetics wasn't a consideration, then it would have been mesh and square, which is undoubtedly the better option.