From nestling to fledgling

Birds, M. C. Escher, 1926

Birds, M. C. Escher, 1926

Every year, spring brings exciting opportunities to observe urban wildlife. Birds are the best subjects because they often tolerate our presence, but their sightings are so familiar that we tend to ignore them. Open your eyes and you will quickly realize you are missing out on some serious action, right at your doorstep. Nestlings and wing-fluttering fledglings are conspicuously begging their parents for food in trees, on the ground, on rooftops and in queerer locations like lamp posts or indoor parkings. They are learning to fly, feed on their own and escape predators and other dangers that lurk at every corner.

For the past ten days I have been spying on a Blackbird (Turdus merula) nest and two Blue Tit (Parus caeruleus) nests. I chose them for their ease of access―low elevation (2-2,5m above ground), no obstruction, close to my home―and the parents’ tolerance, if not indifference, to my presence.

Both species are atricial, which means chicks are helpless following hatching and their survival inside the nest depends entirely on their parents’ intensive care. Born blind and covered with little or no down to keep them warm, they are vulnerable to the weather and defenseless against predators. Nestlings decide when to fledge at their own risk (their parents may entice them by reducing feeds at the nest): once out of the nest, there is no going back no matter whether they can fly or not. Once the chicks have reached the size to fledge, leaving the nest indeed increases their chances of survival.

I wished to witness the nestlings’ great jump into the wild world, but with only three locations randomly visited what were the odds? I was nevertheless optimistic.

The Blackbird’s nest contained a clutch of five chicks. When they are not being fed, which animates them like puppets on strings, featherless chicks look lethargic, but physical transformations occur so fast they seem to be taking place before your eyes. The nestlings were fattening up, growing feathers and getting livelier every day under the attentive care of their parents. My hopes were high to see them fledge.

I was wrong. On my last afternoon visit, all babies were still present; the next morning, all trace of them were gone except for one chick that lay dead at the foot of the tree, seemingly having suffered an uncontrolled fall to the ground.

Adult female (left) and juvenile (right) Blackbird

Adult female (left) and juvenile Blackbird. Credit: Yalakom

It is normal for Blackbird chicks to leave the nest before they can fly, a skill they learn to master within a few days if they survive this particularly lethal stage. Forced to hide on the ground, fledglings are exposed to many hazards, e.g. cars, mower, weather, and make an easy prey for cats, rats, badger, and other predators. Their parents keep feeding and watching after them for about three weeks. By then, the young have reached adult size and resemble adult females, but a number of external features set them apart (brownish beak, chubby appearance, cream spots on the chest, head and the back of the neck).

A few days later, still hopeful, I set out to the public park where the blue tit families had taken up residence in natural tree cavities, a few meters apart from one another. Ten days had elapsed since I had located the nests, seven since my last visit, a considerable amount of time at the scale of a chick’s life. Luckily one of the nest had not yet been deserted. Unlike blackbirds, blue tits nest in cavities, so it is impossible to see the nestlings without video equipment unless they are about to fly away. By chance, the chicks had decided to take their great leap for freedom that Sunday afternoon

A short film of the event taken with my small point-and-shoot camera is available here: Three Blue Tit Chicks on the Loose. Another video of blue tit chicks can also be viewed here.

For an hour or so, I watched the parents relay each other at the entry hole to feed their young. The chicks had to be quite grown up because they sounded really loud, so I decided to stay longer. Soon enough, one chick moved closer to the entry hole; its minuscule orange beak, then forehead and finally its whole head became visible. While awaiting food, it began scanning the horizon with eager eyes. How many chicks were there? I could not tell at this point, but one of them clearly had the advantage.

I realized the cavity had another opening, just above the main entry hole, when a second chick popped out its downy, yellow-grey head. While also showing interest in the outside world, its goal was to reclaim food access which had been monopolized by its sibling for over an hour. It was impossible for the parents to land on the second hole, so the nestling grew frustrated and began gesticulating dangerously on the edge of the hole.

One of the parents feeding the nestlings

One of the parents feeding the nestlings. Credit: Yalakom

By then, two hours had passed and given the increasing agitation inside the nest, I was convinced that at least one chick would jump out or fall off in the next few hours, so, armed with patience, I stuck to my position.

A third chick suddenly joined the second at the top “window” and both started crying in concert. Meanwhile, the first chick, now body half way out of the hole, was itching to try out its little wings. Minutes later, it managed a perfectly controlled flight to a nearby branch. After a snack, it boldly wobbled its way up to the highest tree branches within minutes, as if pushed by an invisible force. A long grooming session ensued.

Attentive spectators of this brilliant scene, the siblings were deliberating when to follow, which took a while. Eventually, the second chick sprang out. It failed to keep on the tree and landed on the ground instead. I watched it carefully while keeping an eye on the third chick, now desperate to get out. Overwhelmed at first, the frail fledgling remained as stone for a few minutes; it then clumsily hopped back to the tree trunk, hid there amidst the high grass and started calling. The parents came to feed the first and third chicks a few times but did not seem to notice the second one.

Blue Tit fledgling

One of the Blue Tit fledglings, a little worried at first, but happy to be off the ground, claws tight on my fingers. Credit: Yalakom

The tree stands in a quiet, shady location of the park, off the pathway. However, on this sunny Sunday afternoon, the place had filled up with families, loud children playing everywhere and loose dogs wandering about. Moreover, the tree is appealing to climb: two kids had played monkey in my presence earlier, shaking the branches and jumping on and off. The chick was so tiny and invisible in the grass that one could have easily stepped on it or otherwise hurt it.

After seeing it go undetected by the parents for long minutes, I resolved to help it up the tree and placed it on the thick branch the first chick had landed on. From there, it ventured higher up, got fed once, but rapidly lost grip and slid back to the ground. At this moment, the third chick decided to abandon the nest, also missing the tree and dropping on the ground. There were now two fledglings to look after which were barely discernable in the high grass. I caught them and put them together on the bulky branch, but before long, both fell off again. Persevering seemed the right thing to do, so I put them back up. This time, they settled in, started a lengthy preening session and the parents came several times to feed them.

After a while, both chicks attempted to crawl up to the tree top again, successfully this time. For an hour or so, the babies were busy preening, eating, napping and scrutinizing their new environment. Everything seemed all right and I was about to leave when a cat emerged from the bush, trotted to the tree and swiftly climbed up the trunk―the chicks were extremely loud! I scared it away and rethought my decision to depart as the chicks were now growing restless again, ready to move on to the next tree. Moments later, one flew to a large tree and the others followed shortly. Relieved, I finally left, hoping that the three chicks would survive their first night out.

Other chicks may have left the nest earlier in the week. Blue Tit clutches can count up to 16 eggs (in woodland areas) although the average is 8-12. Typically, one egg is laid each day and incubation by the female starts once all have been laid, but some chicks may develop quicker and fledge before the others.


REFERENCES

Precocial and Altricial Young (Standford)

Parental care (Standford)

Urban Blackbirds: from egg to independence

Common Blackbird on the RSPB

Blue and Great Tits RSPB Fact Sheet

Blue Tit on Garden Birds

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