Large female, small male
Although female and male peregrine falcons are different, they can’t be easily distinguished at first sight, unlike in most species of ducks for example.
Two types of criteria allowing to distinguish the female from the male. The first type has to do with the feathers, the second with the size.
Let’s start with the feathers: the colour and the pattern of the chest and throat are the best indicators, even if there are individual differences as well. In the case of the couple of the Cathedral, it is easy to see which one is the male and which is the female. The male’s stomach and lower side of the chest is white pink with fine horizontal grey stripes. These are often interrupted. The upper part of the chest and throat are immaculately white, except for a couple of grey-brown spots just above the striped part. The female has a beige-like belly and chest with red accents and with long horizontal dark brown stripes. On her throat there are a lot of brown vertical stripes. Just the area between her “sideburns” and just underneath is completely even in colour; a beige-like tan with red that is easy to distinguish from the white of the male.
The colour around the eyes and that of the naked skin above the beak and the paws (this is referred to as the bird’s “naked parts”) is completely different: in case of the males, they are much more yellowish than with the female.
The criteria for the size are more constant than those of the feathers, but they are also more difficult to evaluate. We preferably compare both partners amongst each other, or with the little falcons. The male falcon is significantly lighter than the female. He weighs between 600 and 650 grams, she, on the contrary, between 950 and 1050 grams. This difference is very important. In any case, it’s not easy to estimate the weight of a bird at a distance. A weight difference also involves a difference in body size and thus in silhouette. Look closely at the picture, one of the falcons is slimmer, his head is very small compared with his body, and he moves elegantly. This is the male! The female has broader shoulders and a larger head. She walks staggering, with a brisk pace. She is clearly more “robust" than the male.
The ultimate test: now that the falcons are 9 days old, the female still succeeds in covering them completely. Not so for the male: he seemed to place himself on top of them in an attempt to protect them against the cold, but without much success.