By Beatrice Obwocha

Few natural sites in the world can match the magnificence and splendour of the pink-rimmed shoreline of Lake Nakuru.

One of the early European explorers wrote of the lake: "The aviary of Lesser flamingos, pelicans and other water birds yonder bewitches the eye and transfixes me for hours to its soft pink reflection."

The flamingos are the main attraction in a tour to Lake Nakuru National Park that also has different kinds of wild animals.

But the number of flamingos keeps fluctuating throughout the year, with the birds dotting the lakeshore at a particular time and then migrating seasonally, leaving only a handful.

When they return, around this time of the year, it is a site to behold.

They often fly back at dawn or dusk in endless uniform columns that could last for days.

Often, after the migration, a large number of birds remain on the lake.

But nature conservationists now say last year’s migration, which happens in November and lasts to in April, revealed a worrying trend, which they attributed to severe drought.

Low water levels caused by a persistent drought between November and March saw the flamingos migrate leaving just about 1,000 birds. These remained and were concentrated at one corner of the lake.

This is in sharp contrast to full aviary that sometimes attracts more than 250,000 birds.

With the ongoing return, already a blanket of pink has been enlarging along the shores of the lake, but conservationists say the numbers are still not near full nest.

The number that flew back to the lake between March and May is estimated to be more than 100,000.

Kenya Wildlife Service (KWS) Central Rift Senior Scientist Joseph Edebe says the number of flamingos had declined due to an increased concentration of salt in the waters of the lake.

A census by KWS last July showed the number of flamingos at the lake was 6,630, down from 258,210 in January the same year.

Dry and low spells

Mr Edebe explains that the number fluctuates during different rain seasons in a year and the birds will stay or move depending on the water levels in the lake.

He says low and high water levels may lead to the migration of the flamingos.

"When the water level is too low during dry spells and too high when it rains, the flamingos will move to other saline lakes," the scientist says.

He says during dry seasons, alkalinity in the water increases due to the decrease of fresh water flowing into the lake from rivers Njoro, Nderit, Lamudiae and Makalia.

"The source of the rivers is the Mau complex and they dried up early due to human activities at the water tower," he says.

Bird food

The high alkalinity on the lake, he adds, is not conducive to production of algae that is food for flamingos.

Too much water is also not good, as it dilutes the alkalinity, thus affecting production of algae.

Edebe says algae grow on precise water conditions and temperatures.

"Thus when the water is too alkaline, there is little algae in the lake and the birds migrate to other salty lakes where they will get food and return to Nakuru when the conditions improve," he says.

Edebe says most of the flamingos migrated to Lake Oloiden in Naivasha and others to Lake Bogoria and Elementaita.

He says between last July and March this year, there was little water flowing into Lake Nakuru, thus the alkalinity was affected and the birds migrated.

He attributed the latest increase in the number of flamingos to the improvement of water quality in the lake.

He says: "The recent rains that have pounded Nakuru and its environs in the past few weeks have diluted the alkalinity of the lake’s waters enabling the formation of algae."

"We at times know the water quality in the lake depending on the number of flamingos present," he adds.

Edebe says pollution of water flowing into the lake also affects production of algae.

According to the KWS official, during rainy season, storm drains get blocked and the water flows directly into the lake, carrying with it toxic substances.

These toxic wastes include fertilisers, agrochemicals from farms, heavy metal from industries in the densely populated Nakuru town and Njoro sub basin.

Human waste from burst sewage pipes also pollutes the lake.

Peak number

According to Edebe, the lake has the peak number of flamingos when there is moderate rainfall, which does drastically alter the water concentration.

The KWS scientist says the trend of flamingos due to the factors stated have changed due to the changing weather patterns.

The lake was too salty in January due to drought and the birds stayed away.

"This explains why there were just about 1,000 flamingos at the lake at that period," he says.