Re siskins. Most siskins will have returned to their north Europe forests to breed. A declining number breed in north Britain's conifer forests.  Another finch that is declining is the twite, also known as the mountain linnet, however it would appear that as the twite numbers fall, the numbers of linnets in upland and north Britain is slighly increasing.  I have not read of any reasons for this, but I would imagine climate change has altered there food sources.