Free information bird houses

free information on how to keep invasive birds out of your nest boxes . use a 1 and 1/8 round hole this will keep invasive english house sparrows out . road side / curb nest box sellers do not care if you get invasive birds in the boxes they sell . invasive birds kill good birds , please do not be part of the problem of why invasive birds out number good birds . See U tube video " bird house oval entrance hole " that oval hole will allow Violet Green swallows in and keep invasive birds out . for more free info if you want to get violet green swallows . email swallows@shaw.ca