We have had Robins nesting in our shed for the past couple of years and have enjoyed seeing them raising their brood but this year the behaviour has been very different.
Initially the robin pair built their nest and seemed to both be feeding the chicks but then I only started to see one parent coming and going. I assumed this was the female that had continued to feed the chicks. Then today outright aggression erupted in the garden and another robin has started constantly harrying the female and physically attacking her.
I carefully checked on the nest and realised that the chicks have fledged and I can see one high up on a shelf where the parent is still feeding it. What I’m wondering now is if the aggressive Robin is the male partner and that now the chicks have fledged he has become more territorial and may be looking to mate or father a second brood - has anyone seen or experienced this change in behaviour once chicks have fledged from a nest?
Re sexing robins, I don't think what you've written rules either in or out.
Re behaviour, it could well be a territory that is now overlapping with another robin. the shed may be a good location to breed, so may or may not be one or both of the same previous years' robins.
It could be that one of the feeding adults has died, and the territory has been opened up a bit for a rival. Difficult to know for sure without leg rings, or distinctive markings etc which often aren't the case with robins.
Sorry should have included some more detail - I know sexing robins can be difficult. The robin that continued to feed the chicks is smaller and duller in colouration than the more aggressive one. The aggressor robin has also frequently been singing and displaying - although I’m aware this is something both sexes will do.
I had wondered had the original male passed away or been killed and that this may be another male moving into the territory which might explain the aggression towards the pre existing nest and parent.
i think your right in that the shed is probably a desirable nesting location - our garden has a lot of undergrowth for foraging and the shed provides good protection from the neighbourhood cats as there is no way for them to gain access.
Just hoping the remaining parent is able to get their chicks fledged successfully as currently the aggression seems to be obstructing them from foraging and feeding for significant amounts of the day.
Thanks. Re sexing robins, I've not heard anything about females being noticeably smaller and duller. This website https://birdhelpful.com/male-vs-female-robins/ is riddled with mistakes, incl mixing photos of American robins (which are blackbirds) with European robins. Unfortunately, websites like that propagate misinformation that can virtually never be challenged directly or corrected. It is an American website written by an American.
Even if the average female (European) robin tends to be slightly smaller, you would be a better judge of size than me by just looking at it, because I've yet to distinguish the two, even when knowing which is which.
One thing that is believed, is (European) robin males are the ones carrying on feeding young after fledging, while females get ready for the next brood. Hard to know if that tilts your surviving adult to being a male, how close to 100% accurate it is. Clearly, after the last brood of the season, it would be 100% inaccurate.
Fingers crossed re youngsters surviving.