Hello all. Welcome to the Frampton Marsh wildlife blog, with me Paige, the practical conservation intern.
After a couple of weeks off I am back to bring you with some interesting wildlife knowledge, however instead of focusing on garden wildlife (which I was doing at the beginning of lockdown), I am now broadening the content. I hope you enjoy!
Precocial and Altricial
Ever heard of these words before? They both relate to the state of a chick or young animal when it is born. A chick that is born altricial means that when it enters the world it does so in an undeveloped state and requires care and feeding from its parents in order to survive. Chicks that are precocial when born are in an advanced state, able to feed themselves almost immediately.
So how do you tell them apart? Altricial birds (also known as nidicolous birds) and precocial birds (also known as nidifugous birds), are easily distinguishable by some physical traits, at the very early stages at least. Birds that produce altricial chicks will generally make well structured nests as the chicks are to live in them for longer, sometimes weeks. These chicks remain in the nest and depend on their parents to feed them, keep them warm and protect them. They are highly vulnerable, born with closed eyes, naked, other than some patchy down feathers, and immobile. These are the chicks you have images of with their mouths open constantly begging their parents for food, with pinkish/greyish skin, that typically look like the birds in the image below. Passerine birds, swallows, woodpeckers and hummingbirds are birds that give birth to altricial chicks.
Precocial birds, born with open eyes and well-developed down cover, leave the nest within only 1 – 2 days after hatching (see image below). Born in an advanced state allows them to walk, run and swim within the first few hours of hatching. However, they are not totally independent and still require help from their parents, as you would imagine. The parents will protect them from predators and although the chicks can feed themselves, their parents will assist them with what and where to eat. Precocial birds include ducks, geese, grebes, waders, gulls and more.
It is thought that there are two main aspects that encouraged these two systems to evolve differently, that being food availability and predation pressure. Precocial species will obtain an abundant amount of nutrient rich resources before laying eggs, which allows them to produce energy-rich eggs to support greater development of the chicks before hatching. In fact, eggs from a precocial birds can contain almost double the number of calories per unit weight as those of altricial birds. This puts pressure on precocial parents to find nutrient rich food sources. Altricial birds do not have the same nutritional demands prior to laying eggs, however, they do have the crucial task of finding sufficient food sources to help their chicks fledge. A disadvantage of having altricial young in the nest, is that the entire brood is extremely vulnerable to predation and is dependent on concealment of the nest and parental defense for survival. Whereas, precocial young, having left the nest early have some ability to avoid predation. This also means that the chance of the entire brood being predated upon is unlikely, increasing the survival rate of the chicks. One advantage to having altricial chicks, although it isn’t the case for all birds, is that both parents can help feed them.
The subject of altricial and precocial development is without doubt much more in-depth, and we have just scratched the surface here. So, if you are interested in learning more, there is a detailed scientific review here that should fulfil your curiosity: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5242088/.
Thanks for reading!
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