Why do baby birds disappear?

One of my regular readers recently asked the question: “Why do baby birds disappear?” We had been corresponding during the recent height of the Australian breeding season. Spring here is coming to a close, but many birds are still actively making nests, sitting on eggs or feeding young in the nest or just out of the nest. This reader observed that many baby birds go missing. What happens to them, she asked.

Here is my reply:

It is very distressing for bird lovers to see the little birds disappear or be killed in some way so soon after hatching or leaving the nest. If we knew the figures, I think we would be horrified by the enormous attrition rate in our fauna, not just birds.

Some possibilities include the following:

1. Removal from the nest by cuckoos. We have several species of cuckoos in Australia. The female lays one egg in a host nest. This could be a thornbill, honeyeater or a range of other species. The host bird hatches the eggs and the baby cuckoo hatches first and it removes all other eggs in the nest in the first hour or so after hatching. It then gets ALL the food from the host parents. Harsh yes – but this is normal, natural cuckoo behaviour.
2. Predation of eggs or chicks: this could be from ravens, crows, currawongs, butcherbirds, hawks and even magpies. Cats, foxes, snakes and lizards, especially goannas, will also raid nests.
3. Predation out of the nest: Once fledged and out of the nest the young birds run the gauntlet of so many hazards including all in number 2 above. Add to those hazards the problem of being hit by speeding cars, wild storms, flying into glass panes (very common), captured by well meaning people and not cared for properly, heavy rain, cold nights and so on.

It is a wonder that any survive at all, especially in urban areas. This is in part compensated for by the following strategies:
(a) Laying 3-5 eggs for each clutch as this increases the success rate
(b) cleverly camouflaging the nest – with all my experience I am still fooled by their cryptic nest sites.
(c) breeding two or three times in one season.

It would certainly help if all cat owners were responsible and made a run for their animals. This would eliminate some deaths in our fauna, but a far greater problem is the feral cats. There is no control of these and all are very big, strong and cunning. I think compulsory desexing of cats is the way to go, but it would only be a start. Catching all the feral cats is probably not feasible. Making sure no more are added to their ranks will be a good start though.

Related articles:

  • Common Blackbirds – the article that started it all. The many comments are very interesting reading.
  • A bit on the nose – an amusing incident involving a cyclist, a swooping Red Wattlebird and a nose.
 

16 Responses to “Why do baby birds disappear?”

  1. [...] Why do baby birds disappear? An article I wrote recently in response to a reader’s question about baby birds. [...]

  2. Helen says:

    Pumba [baby magpie] came into our lives one month ago when we rescued him? from the cricket nets down at the oval. He continues to be very fluffy and he appears to have no interest in learning to fly. At the moment he spends a lot of time sitting in the kitchen watching life go by. Singing happily, eating regularly and telling the dog off.

    Can you tell me when the fluff will go and Pumba will fly away … and leave a little hole in our lives.

  3. Trevor says:

    Hi there Helen, what a cute name for a “pet” magpie! It sounds like he is on a very good wicket living in the house, not wanting for anything and being constantly entertained by all the happenings. No wonder he doesn’t want to leave! I’m just concerned for your dog – I hope he doesn’t get a complex or some other psychological condition.

    The downy feathers on magpies can last for many months, well after they fly independently. I am not sure what you can do to get him to fly off and live an independent life in the wild. He seems to have become bonded to you, your house and family – perhaps not the dog!

    It might be worth checking out your local vet or state wildlife rescue group, such as the one here in South Australia:
    http://www.faunarescue.org.au/

  4. [...] The death rate of young birds can be quite high and most of us would be astounded if we knew the true figures. I have written before about this here. [...]

  5. BirdAdvocate says:

    Thanks for your post. I just checked my Havahart trap in my back yard. There is one more feral cat no longer eating birds.

  6. Trevor says:

    Hi there BirdAdvocate. One less feral cat is a start. Now for the millions of others out there…

  7. Helen says:

    Hi Trevor. Thought I would update you on Pumba. He has learnt to fly … but landing is another thing. He left home last Thursday, choosing a 36 degree day to try life on his own. I didn’t think he would survive. How would he find water? Would other maggies be kind? Would he stand trance-like in the sunlight with his head tilted at a right angle – unaware of cats and cars? Today [Monday] we found Pumba outside in the street, “hiding” conspicuously under a tree. Thin, tired, thirsty but alive. He drank like a fish, ate like there was no tomorrow and has been alseep on his little perch in the kitchen for the past 6 hours. We are all happy to have him home … even the dog.

  8. Trevor says:

    Pumba sounds like a very resilient Magpie to me. Normally Magpies probably get enough moisture from their diet of beetles, spiders etc. Putting out a bowl of water or setting up a bird bath would be much appreciated by all the birds in your garden, especially during the hot summer we are experiencing.

    As for the treatment he will receive from other magpies in the district, one cannot be sure. He may be accepted as that is his natural territory. The real crunch will come next breeding season (from about May-June). In a territorial dispute he might find himself chased off as a threat. Time will tell. Meanwhile enjoy his company.

  9. Caghs says:

    I’m a responsible cat owner (I have a cattery attached to my house, and my three are all desexed, etc …) and I agree with you.

    There’s no reason a cat can’t be completely happy in a cat run, while giving the native fauna a fighting chance. If you’re going to have pets, the very LEAST you can do is make sure they are properly looked after.

    Cats and wildlife can live in peace, if owners take a few responsible steps.

  10. Trevor says:

    Good to hear you are a responsible cat owner, Caghs. If only more people took this stance the birds would have a fighting chance.

    Your comments have inspired me to write a follow up article – but it will not appear on this site for about a month. I am busy writing ahead so I can take a three week holiday.

  11. [...] to thinking – always a dangerous thing. The comment was in response to a post I wrote called “Why do baby birds disappear?” In this article I explained that cats are responsible for far too many bird casualties. One [...]

  12. Michaela says:

    I am a confirmed “dog person”, and I know that cats are a terrible problem for birds and other native wildlife, but dogs can be too.
    I live on a small property near the Grampians and have an enormous number of birds on and near my home. Many Superb Blue Wrens who are pretty tame. Imagine my horror when two little nests, with several well developed chicks (SBW) which I had been keeping an eye on recently were both ransacked and emptied by my old female blue dog. I was devastated and she got a bit of a talking to.
    The nests were low to the ground, one in a calistemon and the other in a grassy thatch under my rose covered pergola. All gone.
    Next breeding season, if I find more nests I will be putting some wire netting around the sites to prevent further problems.

    It’s just in their nature to chomp on small, living, moving creatures,she’s a great mouser too, so they need to be managed accordingly I suppose.
    On percentage I would say cats are much worse, actively stalking and hunting. Whereas, I think my old dog, just took the opportunity as it presented itself. Still very sad and worrying though, as they really are great little birds, doing great work on the insects in my vegie patch!!

  13. [...] Why do baby birds disappear – an article about baby bird deaths. [...]

  14. Trevor says:

    Hi there Michaela,

    Thanks for sharing some of your experiences of birds with my many readers.

  15. Denis Asher says:

    Hi Trevor,

    All support from the Shaky Isles for your efforts re native (correct term) ducks, feral cats (which are a huge problem here, along with their domestic brothers and sisters) and other efforts to support Australian birdlife. It’s always a treat to visit Australia, not least because of your spectacular wildlife (foth flora and fauna) – even the leeches! When will the economists properly measure the dollar value of this to human society?
    But, an amusing story to share with you: the other day, waiting at a local, central city (Wellington) park, I observed a couple tossing corn chips to resident birds, particularly the red-billed gulls (Chroicocephalus scopulinus). The usual melee resulted: every bird in the surrounding area immediately sought out the benefits, including a sparrow (Passer domesticus). Caught up in the excitement, it got too close to a red-bill who snatched it up in its beak in an instant. Feathers flew everywhere as the gull took off, now chased by his mates who saw the chance of another opportunistic snack. The picnickers were shocked and dismayed, like the victim no doubt! Fortunately for the sparrow, shortly afterward his captor had to try and get a better grip, providing his prisoner with the chance to escape: the little blighter took off, wobbly and still losing the occasional feather, but determined and free to resume foraging elsewhere! A lesson learned, no doubt: there’s no such thing as a free meal.

  16. Trevor says:

    Thanks for your fascinating story, Denis. I can just picture it.

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