Friday, 6 June 2014

Progress on my nest boxes

On a previous blog I showed you the boxes I was going to erect in my garden and in the woodland of my neighbours garden. At that stage I had 40 boxes but since then I have made extra. So altogether including the dipper box, I put up 48 with the help of a friend. See

Out of the 48 boxes 18 were made specifically for Marsh Tit, 10 had a 25mm hole and the other 8 had a 23mm hole. In the UK there are only 2 x RAS's at the moment for Marsh Tit. Because of the numbers of Marsh Tit coming to my garden I thought it may be a good idea to start a RAS myself. After talking it over with the BTO I was told I really needed to establish the number of birds that were residing in my area first. I therefore thought that nest boxes suitable for Marsh Tits may give me this important information. Ken Hindmarsh who does a Marsh Tit RAS and comes from Cumbria advised me that a preferred hole size for Marsh Tits was 23mm, the reason being they stop Blue Tits from using the boxes. He was right three boxes with a 25mm hole were occupied by Blue Tits but unfortunately I have not got one Marsh Tit in the remainder.
This is a disappointment and noticeable the Marsh Tits seemed to disappear altogether for about 5 weeks. Why, I do not know, however this last week they are coming again to my feeders, so where have they been? If anyone has got thoughts about this I would love to hear from you.

I have been checking the boxes once a week since 17th April and recording all the information from these checks. The first box to have Pulli old enough to be ringed were the Dippers. No-one was more surprised than me to have Dippers in a box that was only erected on the 14th February.

In the box were 4 Pulli which were ringed at Feather Small on 29th April. The last bird fledged on the 9th May.

One of the hazards of nest box work is the occupation of the Common Wasp (vespula vulgaris) that builds its whitish paper like nest in the roof of nest boxes. It is made from chewed wood fibres mixed with saliva. It often uses abandoned mammal holes, hollows in trees, wall cavities or rock crevices for its nest sites as well.

Many Blue Tits and Great Tits have occupied my boxes. Other than differences in size of the eggs which is minimal they are still difficult to tell apart. The clue obviously is when the adult is on the nest.

These Pulli are Blue Tits which will be ready for ringing in about a week to 10 days

The Great Tit Pulli above were Feather Medium verging on Long so I was able to ring these.
The three pictures above were all taken on the same day and shows the different stages they can be at at any one time.

Blue Tit on the nest and the Pulli are just visible on the left hand side.

Nuthatch often seal the top of the lid to the nest box base with mud. A little care when opening the lid will prevent damage to the mud and should reseal again ok.

Not the same box that the Pulli were ringed from. It shows the type of nesting material used, leaves and bits of bark.

This box of Nuthatch Pulli were Feather Small and there were 6 in the box

A scary hair do on this young Nuthatch!

A summary of my boxes.

48 boxes
19 reached the egg stage,
29 were not occupied.

2 boxes failed
1 Blue Tit and 1 Great Tit.

17 boxes were successful
1 Dipper
7 Great Tit
8 Blue Tit
1 Nuthatch

I obviously need to do some work on the Marsh Tit project ready for next year. Out of the 29 boxes that were unoccupied 16 of these were boxes specifically for Marsh Tits and the other 2 were occupied by Blue Tits


  1. 23 mm is a bit too small for marsh tit. 25 mm is better. With 23 mm some males might not be able to enter. You can make sure blue tits don't take them all by erecting them in pairs, about 6 ft apart. That way, one is much more likely to remain unoccupied. But marsh tits can fight off blue tits anyway, so I guess your boxes weren't used because the birds didn't want to nest in that spot. They have a big territory (at least 2 ha, often 5-6 ha) so boxes at a density higher than that wont get any more marsh tits. They also prefer a small floor area - about 75 x 75 mm. But untlimately, they are picky about nest location, and nestboxes are of limited use - all it does is help the blue tits (possibly at the expense of marsh tits). In a 4 yr trial targetting marsh tits with paired boxes built to mimic natural cavity dimensions, only 14% of pairs used them on average.
    Your 5 week absence will have been due to feeding young, when they tend to forage much closer to the nest (usually within 50 m). Now the young have fledged and dispersed, the adults are moulting so will come back to feeders. Rich B

  2. Hi Richard,

    Thanks for the information, it's appreciated. If nothing else I have learnt something this Spring and that is everything I have done is questionable which is progress in itself.

    A few questions if I may. I will try erecting two boxes 6ft apart with 25 mm holes next year. I have two sizes, the floor area of the 25mm hole box is as you suggest 75x75mm. The problem I have with these is my hands are too big and cannot get inside then. I therefore made some more with 23mm holes and a floor area of 100 x 100mm which from what you say is probably too big, but, I can get my hand in ok. Would a bigger floor area be a problem. I could try 85 x 85mm and see how much room there is for may hand.

    I have sighted the boxes on trees at a height of about 5ft 6ins, being over 6ft I can see in them with the lid up ok. Are these too high? and should I lower them for next year.

    I wonder if my boxes are erected in the right area. Some are on mature trees widely spaced apart with a tree canopy and loads of leaf litter on the ground. Others are erected in an area where there are a few mature trees but lots of scrub trees around as well. The ground is wet/boggy in many places and brambles can be a problem. Between the areas I have just described is a small river dividing them, hence the Dipper pulli on my blog.

    I don't understand what you mean about "boxes at a density higher than that won't get any more Marsh Tits". How many boxes would you erect per hectare or acre.

    From what you say about foraging closer to the nest within 50m tells me that their nesting site is far away from my boxes and I may have no hope of getting any birds interested in any of my boxes no matter what I do.


  3. Hi Charlie,
    Floor area seems more important than hole size (the only reason for a 25 mm hole instead of e.g. 28 mm is to exclude Great Tits). I think 23 mm might be excluding many marsh tits - they're about the same size as blue tits. Use as small a floor area as you can get away with.
    Marsh Tits have big breeding territories, averaging 5-6 ha, with 1.5 ha as the absolute minimum. So if you have more than one box (or pair of boxes) in a territory then it's a waste, as you can't get two pairs using them - their territories wont allow it. Boxes at a density of about 1 box (or pair) per hectare are a good compromise of upping your chances of marsh tits (giving them a couple of choices per territory) but not inflating blue tits by flooding a wood with boxes.
    They seem to like mature trees with a bit of scattered bushes for the nest site - they often tend to nest in younger trees, so I put my boxes on trees about as thick as my leg, at a height of 0.5-1.5 m - lower boxes also discourage blue tits.
    But to be honest, boxes do seem to be a waste of time. They can't increase marsh tit numbers (as the territories can't get any smaller, unlike blue tits), and uptake is so low that it's a lot of effort for little return.
    I've just finished a 2-stage nestbox trial - one using 15 pairs of normal boxes with a 25 mm hole, and another using 37 pairs of small-floor boxes with 25 mm hole. These were all placed in known marsh tit territories, and most of them near known nest sites. But in the first trial I got just 1 nest in a box over 5 years, and in the second I got 10 nests over 4 years. And that's out of nearly 70 possible pairs of birds. So it was worth trying, but not worth the effort in the end - they're just very picky about what they want and where! Other nestboxes schemes in UK have also only had uptake of less than 10%. So you might get lucky now and again, but you wont get many.
    Hope that helps. Rich B