We’ve all failed to differentiate between glass and air and collided with a door or window.
And, in the garden, we’re not the only ones who don’t mix well with glass.
The RSPB is warning that thousands of birds will injure themselves in the forthcoming breeding season by striking windows in the heat of the chase fight off a rival and attacking their own reflected image in confusion.
The wildlife charity is asking people to reduce the risk of window strikes and the associated injuries in the coming months such as concussion, broken beaks and internal injuries.
The onset of spring has triggered a flurry of activity with our wild birds as they prepare for the breeding season.
Territorial birds seemingly attack or fly at windows or reflective surfaces as they see themselves in the glass and think it is an intruding bird and try to defend their patch.
Some birds also collide in the heat of a chase or because they see a reflection of the sky and trees in the glass. There may also be another window or mirror in the room making the bird think there is a way through.
The RSPB is advising that the risk of window strikes can be reduced by making the window pane more obvious to the bird, or by removing the reflection.
The wildlife charity suggests fixing an object to the outside of the glass to indicate the obstacle. Any image will work – try cutting out random shapes such as half moons or stars from coloured self-adhesive plastic.
The most effective shape is likely to be a hawk, as the short- headed long-tailed silhouette of a bird of prey creates the instinctive reaction in small birds to avoid it.
You could also put cling film or non-reflective cellophane on the outside of the window during the breeding season to stop persistent attackers.
More expensive, but highly effective, are vertical blinds which can be angled so that you can observe your garden whilst reducing dramatically the appearance of the windows as a flight path.
Lloyd Scott, RSPB Wildlife Adviser, says: “Birds will do anything to defend their territory and at this time of year when they are setting up territories and breeding, window strikes are common.
“We know ourselves that when we’re in a hurry or not paying attention it is easy to walk into a glass door and give yourself a bit of a headache!
“Birds can be knocked out, break their beaks and smash their skulls, or suffer concussion or internal injuries.
“It is very unpleasant for the birds and disturbing for us when we realise what has happened.
“There are various simple things you can try to reduce the risk of this happening and silhouettes on windows are a great place to start. I suppose they are like scarecrows for windows.”
The popularity of patio doors and double-glazing has led to many injuries and fatalities among birds that fly into them.
Double glazed windows tend to pose a greater risk than single glazed, since they produce clearer reflections.
If you find a bird that has flown into a window, put it in a dark, safe place to rest for a couple of hours for the best chance of recovery.
Self-adhesive bird silhouettes can be purchased from any RSPB shop, many good pet shops and garden centres.
For ideas visit www.rspbshop.co.uk