CBC Chat Forum Thread

AuthorTopic: A plea to check your nest boxes.
Noel Elms A plea to check your nest boxes.posted at 23/05/2013 12:11:22

Obviously too soon to draw definite conclusions but the indications are, from both my own garden nest boxes and natural sites elsewhere, that a higher than normal number of eggs have either not hatched or become damaged in the nest and also that clutch sizes may be smaller. Calcium is vital to the success of breeding birds both for egg shell production and healthy chick growth and with the all too evident lack of invertebrates this year, hen birds may not have been able to 'top up' the level of calcium in their body just prior to laying.

Some studies suggest that the soil in worm gut and other soil dwellers, such as millipedes and woodlice, has a higher calcium content than snail shells and further suggest that garden soil may have a high calcium content. It would be interesting if a comparison could be made between the productivity this year  in garden and non-garden nests.  Those of you who do not already submit data to the Nest Record Scheme, may like to check your nest boxes or indeed any nest, once vacated and join me in posting their findings on this Forum.

My thanks in anticipation.

Noel.

Tom Green Re: A plea to check your nest boxes.posted at 23/05/2013 21:05:27

Noel
Thanks for your interesting 'article' I recall that my parents always had grit (? shells) available for our hens. Out of interest which other species of birds augment/get calcium if at all, from grit/shells?
Would it be naiive to ask whether calcium availability might be higher in calcareous areas such as Norfolk rather than, say acidic soils/rocks ?

PS Have yet to put up nest boxes in our 'new' garden in Blakeney, but will ask around the neighbours - Tom Green

Noel Elms Re: Re: A plea to check your nest boxes.posted at 24/05/2013 07:50:51

Tom.

My thanks for offering to check the neighbour's nest boxes, I look forward to seeing the results.

I'm open to correction here but I believe all birds have a gizzard and thus need to take in grit in order for the muscular stomach to work efficiently. It seems to me that the level of calcium intake by this means would depend upon the calcium content of the material ingested. It also seems to me that calcium availability would be higher in calcareous soils, perhaps the geologists or avian nutritionists among us may care to comment.

Noel.

Tom Green Re: A plea to check your nest boxes.posted at 23/05/2013 21:08:42

Noel
Thanks for your interesting 'article' I recall that my parents always had grit (? shells) available for our hens. Out of interest which other species of birds augment/get calcium if at all, from grit/shells?
Would it be naiive to ask whether calcium availability might be higher in calcareous areas such as Norfolk rather than, say acidic soils/rocks ?

PS Have yet to put up nest boxes in our 'new' garden in Blakeney, but will ask around the neighbours - Tom Green

Noel Elms Re: A plea to check your nest boxes.posted at 23/11/2013 16:23:03

In the absence of any information from within the Cley Square, please bear with me in providing an update to my original post based on data from elsewhere.

Too early for a final report to be compiled but anecdotal evidence from BTO Nest Record Scheme participants suggests that in the case of the two most common nest box users, Blue and Great Tit, box occupancy was lower than usual. First egg dates were 2-3 weeks later than usual and clutch sizes variable. Incubation periods were longer than usual and when the eggs did eventually hatch, growth rates were slow and a higher number of nestlings than usual died in the box. Growth and survival rates of caterpillar-dependent nestlings were generally low this year and not confined to box-nesting species.

Further evidence indicates that Great Tits and probably Blue Tits may unusually, have had second broods which were more successful. This may explain the above average number of juveniles trapped in my garden in July.

Noel Elms.

Andrew Cannon Re: Re: A plea to check your nest boxes.posted at 25/11/2013 18:46:45

Hi Noel et al
Received wisdom, as you know, is that Blue & Great Tits don't second brood in this country, but can second clutch if they lose a clutch sufficiently early that they judge re-laying worthwhile. This year, however, I wouldn't put anything past them as I personally saw something I've never heard of before. After cupping and lining her nest, and waiting and waiting to lay, the Great Tit on our camera box at Natural Surroundings eventually settled down to incubate - a completely empty nest! I was in a quandary what to do, technically illegal to disturb her even for her own good. After nearly a month, twice the usual incubation period, and looking pretty scruffy, she finally gave up and abandoned her nonexistent eggs.
All the boxes in our wood failed yet, just as you say, there seems to be plenty of juvs about now so they must have bred somewhere, sometime. Altogether a most peculiar year.
Kind regards
Andrew Cannon

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