Wednesday, 18 March 2015

haywire

It has been a strange winter, with 30-degree temperatures in the last week of November, which is unheard of, and higher than average temperatures throughout the last three months. It’s unlikely that we’ll be needing any of our heaters this year. It has also been much wetter than usual, with humidity so high on occasion that condensation has been running down the walls. Hours of sunshine have been well below average. It’s all down to El Niño.

El Niño is a climatic phenomenon that occurs every five years or so. It manifests itself as an anomalously warm plume of surface water along the equatorial Pacific, and the name derives from its tendency to appear around Christmas. This warm surface water blocks the upwelling of nutrient-rich cold water off the west coast of South America, and it can last up to a year.

The El Niño phenomenon is closely linked to the position and amplitude of the Rossby waves in the circumpolar jet stream, which this year has led to record snowfalls in parts of North America, although which is cause and which is effect is not well understood. However, this post is not an attempt to explain but is merely an account of some of the strange goings-on that I’ve noticed this winter in Hong Kong.

Mile-a-minute is an alien vine that may not spread as quickly as its name suggests, but it nevertheless propagates at a prodigious pace. Fortunately for the native vegetation, it’s an annual, and it’s usually in full dieback mode by mid-October. However, the following photo of the tree opposite my house shows an explosion of new flowers; it was taken in mid-November In fact, I noticed some sporadic outbursts of new flowers as late as the first week in February!


Similar anomalies include the acacias, which usually flower in late April. This year, however, many trees were putting out flowers in early February, although the total coverage on a single tree was never more than 1 percent (an individual acacia usually carries thousands of tiny yellow flowers, as shown in the following photograph, also taken from my balcony).


Cotton trees are one of the few species to shed their leaves in autumn in Hong Kong. Not this year though. Flowers usually appear on the bare trees in late February. Flowering was on time, but it did look strange to see so many old leaves among the flowers.

It may simply have been the warmer than average weather, but insect activity has been quite noticeable over the winter (there is none in a normal year between December and March). Crickets, cicadas and ‘clickety clackers’ have been making themselves heard on many winter evenings (I have no idea of the true identity of the last of these, because although the sound they generate is distinctive, I’ve never actually seen one).

I’m not sure if any of the avian activity I’ve witnessed over the last couple of months is atypical, but I have noticed a few things that have struck me as odd. The courtship ritual of the spotted dove is one of the most comical to be seen in Hong Kong, and it is usually a common sight at this time of year, but I’ve seen only two examples thus far this year, and in one of those it was the male that lost interest (in normal conditions, it’s the active disinterest of the female that makes the ritual worth watching in the first place).

Other bird-related observations may relate to year-to-year fluctuations in the population of a species rather than the baleful influence of El Niño. For example, at the turn of the year I had the sense that there were more red-whiskered bulbuls about than normal, and I also felt that their songs were not quite what I’d previously thought was standard. Two years ago, I wrote about their distinctive four-note song and wondered why they didn’t sing the notes in a different order. Well, they haven’t changed the order, but this year I’ve noted a few nonstandard variants based on those four notes. For example, an additional, shorter, note has often been inserted between the first and second original notes, or between the third and fourth. Sometimes I hear both insertions. Yet another variant is to omit either the first or fourth note, making it a three-note song. Perhaps the strangest of the ‘new’ songs is a three-note song repeated, the approximate cadence being tum-ti-tum[pause]tum-ti-tum. The second triplet is at a lower pitch than the first.

Other markers of spring have not been out of the ordinary. I heard the first koel of the year on 17th February and the first large hawk cuckoo on 14th March. Both are now in full ‘shouting’ mode.

Has anyone else noticed unusual behaviour in their parts of the world? If so, do please leave a comment. I’m particularly interested in hearing about the activities of plants and animals rather than unusual weather patterns, but news of anything that strikes you as bizarre will be welcome here.

update
The acacia opposite my house started flowering again in late April, when it’s supposed to, but the total flower output was less than 5 percent, and if the acacias in the photo above did flower again, it wasn’t possible to detect this from a distance of 50–60m.

Flame trees, another ornamental tree that has been introduced to Hong Kong, usually start flowering in the second week in June. The following photo was taken on 15th May.


update: 28/12/2015
The Hong Kong Observatory declared an El Niño event more than a year ago, which should mean that things are getting back to normal now. But they aren’t. Last month was the warmest November since records began in 1884, with an average 2.5 degrees Celsius above the long-term average. This may not seem much, but we are comparing averages, so 2.5 degrees represents a considerable deviation from the norm. And the mean temperature for the month was 24 degrees, which would be a hot afternoon in a normal November.

El Niño usually lasts only one year, so I was surprised to learn, a couple of months ago, that droughts in some parts of Africa, and floods in others, were being linked to this phenomenon. However, this has already been one of the strongest El Niños on record, so I shouldn’t be surprised if it lasts well into a second year.

Here in Hong Kong, the situation has developed from strange to bizarre. Several tree species have been flowering in recent weeks, including the acacia in front of my house, which would normally be flowering in April:


The flowers in this picture represent less than 5 percent of the normal flower load, but any flowers at this time of year are not to be expected.

A similar situation exists with respect to flame trees, which usually flower in June. The following photo was taken in early November, and once again it represents only a tiny fraction of the normal flower load:


The next photo was taken around the same time and shows a cluster of paper-bark trees in flower. Trees of this species can flower at any time between late spring and the start of autumn, but these trees are significantly late.


Perhaps the most bizarre event of all happened on 8th December. Magpie robins are around all year, but they usually sing only in spring, and all you will usually hear at this time of year are threat calls. However, on this day I heard a full-on, this-is-my-territory song from an obviously confident individual, and a few hours later I spotted three males chasing each other through the branches of the acacia, pausing occasionally for short bursts of song. This turned out not to be a one-off event, because on 27th December I returned from shopping to be greeted by another virtuoso performance, almost certainly not by the same individual.

No comments:

Post a Comment

Please leave a comment if you have time, even if you disagree with the opinions expressed in this post, although you must expect a robust defence of those opinions. If you don’t have time to comment but enjoyed the post, please click the +1 button on the right-hand sidebar (near the top of the page).