Tuesday 26 April 2016

Inexperienced parents: I just don't buy it!

A common reason offered for the failure of a pair of garden birds to successfully raise a brood is that "...the parents are probably inexperienced..."

This view seems to be so widespread, that even the good folk on BBC SpringWatch have been known to offer this explanation.

But surely this is another example of people dreaming up a simple theory without thinking things through...

So what is my case for suggesting that the "Inexperienced Parents" notion is just nonsense?

Let's take the little blue tit as an example garden bird, as this is probably the nest box species most familiar to us.

It's dangerous out there

Whichever figure you take for blue tit life expectancy (and there are many on the internet to choose from) the blue tit's life is dangerous and short. If a blue tit survives its first 12 months (and most do not), it may be lucky enough to find a mate and raise a brood.

While some individuals have been recorded as living 10 years or so, this is very unusual. Most die within the first couple of years, so the vast majority of blue tit parents will be 1st or 2nd year mums & dads.

The miracle of life

Like most animals (and many humans) blue tits don't set out to be parents.

They are driven by their hormones to mate. But the process does not start when they mate, they are first driven to find a partner but not mate straight away.

At a certain time of the year, they search for a mate, find a nesting location, build a nest to a particular design and then they mate. The female starts to sleep in the nest over-night after mating, so any eggs she lays in the early hours of the morning are deposited in a relatively safe place.

After a certain number of eggs have been laid, she starts to warm them up. The chicks hatch a couple of weeks later, at a time that seems to correspond with the "green caterpillar harvest".

Both parents then feed the chicks with what they need, taking care to remove and dispose of fecal sacs some distance from the nest, so as not to draw the attention of predators. Once the chicks have left the nest the parents continue to protect and feed the chicks for a few weeks.

How amazing is that?

Well it is so amazing and so automatic that we can only deduce that the whole sequence is deeply embedded in the bird. If it wasn't automatic then the process would fail most of the time. The parents would mate at the wrong time, lay eggs before the nest site was selected, there wouldn't be enough food available, and any chicks would probably perish.

Actually it is not just amazing, its miraculous!

Can blue tits learn stuff?

Sure they can. They can learn to open seed and nut cases, peck at milk bottle tops to get to the milk, and eat from man-made garden bird feeders. They can learn that some birds can be aggressive and will jab them with their beaks if they don't give way. They can find food sources, remember the location and revisit them from time to time to check if they have been replenished.

It seems quite natural that birds should be able to learn day-to-day tasks. Even the gold fish in our pond can remember that I am a source of food and I only feed them in one particular spot in a corner of the pond (however, they forget this over winter and have to re-learn it during the spring).

Hmm, what can I use this for?

But it is a completely different proposition that a blue tit will learn something from a clutch of chicks that die. And that (somehow) will do things differently in 12 months time! Even when human babies die, we often have no idea why, so don't get much of a chance to vary our behaviour.

We are all natures little experiments

All creatures, whether blue tits or people, are unique experiments. Within any species there is a variation or spread of behaviour. The automatic responses may conform to a "norm" in most cases, but there will always be a few individuals whose "blue-print" is a little odd.

For example, some individual birds spend a lot of time "fighting" with their own reflection in windows. Its not the norm, but if this disturbing behaviour offered some kind of advantage, then this trait may become the norm through breading with other shadow boxers.

Driven by our DNA

In the past I have suggested that small birds which host a cuckoo must be incredibly stupid. But I now think these foster parents realise what has happened long before their baby out grows them. They just can't stop themselves from feeding the chick because their in-built response to an open beak is just too strong.

It is similar to reports of non-parent birds (especially wrens & robins) feeding the chicks of others.

Summing up

As blue tits and other small garden birds generally have a short life, it is more reasonable to suggest that they are driven by their hormones when it comes to the whole incredible (and improbable) sequence of producing off-spring. Since most individuals only get one or possibly two attempts at it in the whole of their short lives, there is no room for error. No room for learning on the job.

Chicks often die in the nest, and when viewed through a camera it is impossible for the observer to identify the reason. It can often look like parental neglect, but we can't see what the adult bird can see. It is more likely due to a lack of available food sources, illness or disease, than a gap in the knowledge of the parents, which some people choose to put down to inexperience.

So next time someone on SpringWatch plays the "inexperienced parents" card, I'd like Chris Packham to step in and say "I'm sorry I am going to have to stop you there, because you are talking nonsense!"

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