Does the arrival of the Pied Cuckoo herald the onset of the monsoon? The Pied Cuckoo Campaign was launched in 2009 to collect information to assess this age-old belief.

More than 600 sightings of this wonderful migrant have been contributed by over 200 MigrantWatchers so far; the first sighting dates among these were compared to monsoon arrival, as available with the Indian Meteorological Department (see the graph alongside). Each dot shows the earliest Pied Cuckoo report (after 1 May) for a broad location (an area roughly 200 Km across).

The results are fairly clear: Pied Cuckoos arrive before the monsoon in most parts of central and northern India (they are resident in southern India). You can see this from the pattern that most dots in the picture to the right are below the dotted horizontal line.

But the degree to which the arrival of the Pied Cuckoo precedes the monsoon varies from place to place, as can be seen from the scatter of the dots within each year. And even for the same general location, this varies from year to year (see how the coloured dots are in different places in different years).

What appears to be happening is that, where the monsoon arrives early, Pied Cuckoos arrive a few days before monsoon onset; but where the monsoon arrives late, the cuckoos arrive well in advance of monsoon onset.

So, overall, the old belief is true, and Pied Cuckoos tend to arrive before the monsoon — but to different degrees, depending on when the monsoon begins at each place.

Also see this article on Pied Cuckoo migration.

Rohan Chakravarty draws wonderful cartoons based on green themes. One, from a few days ago, is about How the Pied Cuckoo brings monsoons to India. Do take a look, and while you are there, check out his other bird cartoons, including the one describing 11 types of birdwatchers. As Rohan asks: which one are you?

Today’s edition of The Hindu has an article by KS Sudhi about the Pied Cuckoo Campaign of MigrantWatch. Do take a look.

Also, the photographer of the lovely Pied Cuckoo image is not mentioned. He is Rohan Kamath, whose MigrantWatch sightings you can see here. And here are his photos on India Nature Watch.

In the Pied Cuckoo campaign, MigrantWatchers have contributed 363 sightings of this wonderful species so far (until 15 July 2011). A summary of these sightings from places to where the Pied Cuckoo migrates shows that it does, by-and-large, arrive in advance of the monsoon, but the exact dates are variable.

To illustrate the general pattern of migration of this species, we have put together this animated map, which shows the progression of Pied Cuckoo migration across the country in advance of the monsoon.

This animation has been made by selecting March-to-July sightings from all Pied Cuckoo reports in the MigrantWatch database between 1 July 2007 and 15 July 2011. To compare these sightings with the onset of the monsoon, we have also added in lines depicting the normal onset of the monsoon (digitised from a map available from IMD Pune).

In March and April, almost all sightings are from southern India, where the species is known to be resident year-round. This remains so until the middle of May. In the third week of May, the first migrant sightings appear, in the West and the North-east. As the monsoon hits the Andamans, the first birds in northern India are seen. More and more birds are subsequently seen across the West, North and East. By the time the monsoon reaches Kerala (in the first week of June), Pied Cuckoos are everywhere, except perhaps the extreme West and North-West.

Where are the gaps in information? Do you see patterns that would be interesting to follow up? Do leave a comment below.

Thanks, of course, to all MigrantWatchers who have contributed their Pied Cuckoo sightings!

By Suhel Quader and Uttara Mendiratta from the MigrantWatch team

In 2010 we continued the Pied Cuckoo Campaign, an effort started in 2009 to gather data that would help understand the association between the southwest monsoon and arrival of the migratory population of the Pied Cuckoo to the Indian subcontinent from Africa.

Many people believe that the arrival of the Pied Cuckoo precedes the onset of the monsoon by 1–2 weeks. Is this indeed the case? The Pied Cuckoo campaign was started precisely to answer this question.

Mousumi Dutta, a MigrantWatch participant who works for the Indian Meteorological Department presented an analysis of the 2010 Pied Cuckoo data earlier on this blog; and a year and a half ago, we summarised the findings from the first season of the Campaign.

In this post, we compare the 2009 and 2010 sightings of this species in relation to the onset of the monsoon in these years. (For details of how we filtered and analysed the data, see Details, below.)

The monsoon in 2009 and 2010
The ‘normal’ onset of monsoon on the Kerala coast is 1 June. In 2009, the monsoon arrived 9 days earlier than this; and in 2010, it arrived 1 day earlier than normal. After the onset, cyclones disrupted the normal progress of the monsoon in both years. In 2009, a cyclone in the Bay of Bengal slowed the monsoon’s progress despite an early start across southernmost India, West Bengal, and the northeastern States. In the beginning of June 2010, cyclone ‘Phet’ in the Arabian Sea brought rain to parts of western India, but delayed the northward progress of the southwest monsoon.

Pied Cuckoo sightings in 2009 and 2010
Between 1 May and 15 July, the number of sightings of the Pied Cuckoo reported to the MigrantWatch database was 28 in 2009 and 25 in 2010.

Despite the earlier arrival of the monsoon in 2009 than in 2010, the first sightings of the Pied Cuckoo were on similar dates in both years (17 May and 18 May from Kolkata and Alibag respectively in 2009; and 16 and 17 May from Bhubaneswar and Jalpaiguri respectively in 2010).

First sightings are shown in relation to monsoon arrival in the maps below. These maps show ‘isolines’ (connecting locations with similar monsoon arrival dates) that depict the approximate advance of the monsoon in the two years (simplified and redrawn from maps issued by the Indian Meteorological Department). The coloured points show the locations and first sighting dates of Pied Cuckoo reports submitted to the MigrantWatch database. Twelve of the points have numbers beside them – these are locations for which first sighting dates are available for both 2009 and 2010. These points are: 1-Ahmedabad, 2-Bhubaneswar, 3-Chandigarh, 4-Jaipur, 5-Jalpaiguri, 6-Mount Abu, 7-Mumbai, 8-Nagpur, 9-New Delhi, 10-Panchkula, 11-Pilerne (Goa), 12-Pune.

To examine more closely the relationship between monsoon arrival date and Pied Cuckoo sightings, we show a scatterplot of the relationship below. Each point represents a location for which we have both the first sighting date and the approximate monsoon arrival date (taken from the IMD maps). If a point falls on the solid diagonal line it would mean that Pied Cuckoos were sighted on the date of monsoon arrival at that location; if on the dashed line, 5 days before; and if on the dotted line, 30 days before the monsoon arrived. So, if Pied Cuckoos are good at anticipating the monsoon, we would expect the points to march from the lower left to the top right of the plot. If you click on this graph you will see a larger version, on which twelve points are numbered just as in the map above.

The maps and scatterplots suggest that the degree to which the arrival of Pied Cuckoos precedes the monsoon is highly variable. Sometimes the earliest sighting is no more than a few days before the monsoon arrives, and sometimes the earliest sighting precedes the monsoon by more than 30 days. So Pied Cuckoos often do arrive at a location before the monsoon does, but the degree to which they do so varies with location and year.

Let’s look at the 12 sites for which we have first sighting dates in both years. The monsoon arrival dates and the first sighting dates from these sites are shown below, with points from 2009 in black and those from 2010 in red. The points for a single location are joined by a line to show how the arrival of the monsoon changed in the two years; and consequently how Pied Cuckoo sighting dates changed. Again, the numbers correspond to the numbered locations on the maps, above.

To help interpret this graph, the two asterisks joined by a dashed line show what one would expect for a hypothetical situation in which the Pied Cuckoos adjusted their arrival perfectly with changes in monsoon arrival — we would see a line pointing upwards from left to right. (For a more comprehensive pictorial and verbal description for how to examine this graph, click here.)

What do we see in the actual data? Out of the 12 locations for which we have information, 6 lines point upward and 6 downward, which means that cuckoos appear to show no consistent differences in arrival date with differences in monsoon onset!

Does this mean we have to revise our dearly-held beliefs about the impeccable timing of Pied Cuckoo migration? Let us know your thoughts in the comments.

Acknowledgements: The most important people in creating this report, as in all of MigrantWatch, are the participants who contributed their time and effort in reporting sightings to the database. This link lists all those whose sightings of Pied Cuckoos between May 2009 and April 2011 were uploaded to MigrantWatch. MO Anand helped in various ways with the preparation of this report. We are grateful for comments from Umesh Srinivasan and R. Jayapal.

First arrival of the Pied Cuckoo in 2010 in relation to the onset of the Southwest Monsoon

by Mousumi Dutta

Mousumi Dutta is a frequent contributor to the MigrantWatch database. She is an avid birder, and spends her spare time on bird and wildlife conservation. She works with the Indian Meteorological Department, and so has a particular interest in bird migration. Mousumi’s MigrantWatch sightings page is here.

India’s climate is dominated by monsoons. Most of its annual rainfall (86%) occurs during the Southwest monsoon months. The monsoon is a key influence on agricultural output as well as the overall economic growth of India. From ancient times it has been believed that the onset of the monsoon is associated with the appearance of the Pied Cuckoo Clamator jacobinus.

The Southwest monsoon normally sets in over Southeast Bay of Bengal on 20 May and then over Kerala on 1 June. An analysis of the first sighting dates of the Pied Cuckoo and the onset of the Southwest monsoon for the year 2010 (see figure below) shows a fairly systematic pattern. In general, the first sighting of this species in a State is 20-25 days in advance of the onset of the monsoon in that State. This appears to be earlier, relative to the monsoon, than reported for last year.

These patterns indicate an interesting relation between the onset of the monsoon and the arrival of Pied Cuckoos. Long term studies are needed to clarify the details of the relationship between the monsoon winds and Pied Cuckoo migration.

Methods
First sighting dates (after January 2010) for Pied Cuckoos for each State were taken from the MigrantWatch database. (Maharashtra and the four southern States were excluded.) Dates of the onset of the monsoon for each State are taken from the Indian Meteorological Department’s monsoon pages (click on “Northern Limits of Monsoon”). The data used to generate the figure are given below. The links under “Reported by” point to the sighting page on MigrantWatch.

If you would like to make your own visualisation and analysis of Pied Cuckoo sightings, you can download all 300+ records here. Please share your findings with everyone at MigrantWatch – send us (mw@migrantwatch.in) a small blog post and we will put it up.

In several cultures and folklores across India, the Pied Cuckoo is believed to herald the onset of the southwest monsoon. In May 2009, MigrantWatch started a Pied Cuckoo Campaign, in which birders from all over India were asked to report first sightings of this species. Does the Pied Cuckoo arrive before the monsoon sets in in different parts of the country? Does the monsoon arrive at a consistent interval after the first Pied Cuckoo is seen? These are some of the questions the campaign set out to address.

The campaign was taken up enthusiastically by MigrantWatch participants, with over 100 Pied Cuckoo entries to the database for 2009, and additional records from previous years. (All data collected during this campaign can be accessed on the MigrantWatch website after you login to your account.)

So did the Pied Cuckoo announce the arrival of the monsoon in different parts of India in 2009? Here are two visual depictions of the arrival of the cuckoo and the monsoon.

The 2009 monsoon
The monsoon set in nine days early on the Kerala coast (on 23 May instead of the normal 1 June) and made a good start. A cyclone in the Bay of Bengal disturbed the normal pattern just after it set in. By 25 May the southwest monsoon had moved over entire Kerala and Tamil Nadu, parts of coastal Karnataka, northeastern states, and most parts of West Bengal. Despite an early beginning, the monsoon progressed slowly after the beginning of June.

About the map and graph
The map shows ‘isolines’ (connecting locations with similar monsoon arrival dates) that depict the approximate advance of the 2009 monsoon (redrawn from this map from IMD, Pune) and the first arrival dates of the Pied Cuckoo as reported by MigrantWatch participants from locations across India.

The graph shows a scatterplot of monsoon arrival dates on the X-axis (horizontal) and first sightings of the pied cuckoo on the Y-axis (vertical). Each point corresponds to a location for which a Pied Cuckoo sighting was reported. The solid black line shows where one would expect the points to fall if each first sighting of was on exactly the day that the monsoon arrived at that location. The dashed black line indicates first sightings preceding the monsoon by five days, and the dotted black line 30 days.

Monsoon arrival dates were extracted from the isolines shown on the IMD Pune map.

For both the map and the scatter plot:

• Only sightings before 15 July 2009 have been used.
• Only the earliest sighting was used for locations with multiple sightings.
• Because there is a resident population of Pied Cuckoos in southern India, we excluded all sightings south of 15°N latitude; but we made an exception for Rishi Valley, Andhra Pradesh (13.6°N), where the species is known to not be resident.<1>

What can we infer about Pied Cuckoo migration? Might the unusual monsoon this year have altered the typical pattern? Please do write down your interpretations as comments to this Blog. If you would like to look at all sightings of Pied Cuckoo in the 2009 season, you can download them here in excel, open document format, or as a comma-delimited text file. Please also read the notes accompanying these sightings.

Note
1. It is still not clear where exactly in southern India this species is resident and where migrant. The various handbooks and field guides on Indian birds differ on this. You can help to resolve this issue by entering General Sightings of Pied Cuckoo from any time of the year into the MigrantWatch database.

Edits
This post was edited on 20 October 2009 to remove an erroneous May record of a Pied Cuckoo from Rajasthan. This record has been removed from the figures as well as the accompanying data files.

by R. Nandini and Sanjay Sane

In popular folklore the appearance of certain birds is considered to herald the approaching rains. But there are other, less conspicuous, organisms whose arrival often goes unnoticed. Migratory insects of several species arrive in the thousands, either alone or in swarms, staggered across the days preceding the arrival of the rains.

In a recent paper that generated headlines worldwide, Globe Skimmer dragonflies Pantala flavescens (also called Wandering Gliders) were discovered to have the longest insect migration route recorded so far – a roundtrip flight between India and Africa with stopovers in the Maldives and the Seychelle islands.

Charles Anderson, reporting his findings in the Journal of Tropical Ecology <1>, recorded the arrival and departure of dragonflies in southern India, Maldives and West Africa over a period of fourteen years, with Malé, Maldives being the focal site. Dragonfly occurrence (particularly P. flavescens) in Malé began in October, peaking between November and December, coinciding with the east-bound high-altitude winds (~ 1000 m asl) of the Inter-Tropical Convergence Zone (ITCZ <2>).

Putting together dates of arrival across the study sites as well as the duration of residency of dragonflies at Malé, he reconstructs a steady north-south movement of dragonflies from southern India through the Maldives across 500-1000 km. A second wave of dragonflies was recorded in Malé between April and June, coinciding with occurrence of the Somali Jet, a band of fast low-lying southwesterly winds over the Arabian Sea blowing from Africa to India.

While this study was focused on dragonflies, Anderson also reports some information on birds, and found that the pattern of bird arrival in the Maldives mirrored that of the dragonflies, peaking between November and December. Among the bird species he reports as crossing the Western Indian Ocean are the Pied Cuckoo, Lesser Cuckoo, Eurasian Cuckoo and the Amur Falcon.

Collating available information on the migration of birds like the Amur Falcon, wind patterns like the ITCZ and Somali Jet, and records of occurrence of certain species of dragonflies at specific times of the year in the Maldives and India, Anderson hypothesizes that dragonflies, like some species of birds, possibly migrate in a loop from India over the Maldives and Seychelles to east Africa (Tanzania or Kenya) and then back again to India. The ITCZ is known to travel across the African continent, bringing rains to different parts of Africa over the year <3>, and insect, including dragonflies, are reported to migrate with these winds. Anderson suggests that, once in Africa, Globe Skimmers probably move southwards and then loop back north to equatorial east Africa before leaving the continent on the return migration to India.

In all, this incredible circuit would cover a total distance of 14,000-18,000 km, with 3,500 km over the open ocean, and would span possibly four generations of dragonflies.

How could insects only a few inches long undertake journeys that span their own body lengths several million times over? On the face of it, this implies deterministic and purposeful flying, as well as knowledge of which winds to harness to get to a destination. Anderson proposes instead that dragonflies need only rise upwards, encounter a passing wind and then largely soar or glide along this wind till they reach land. If this simple explanation is indeed the way in which dragonflies cover these enormous distances, how will such behaviour be affected by phenomena like global warming, which is known to alter the intensity and speeds of winds like the Somali Jet <4> and the ITCZ?

Dragonflies are reputed to be powerful fliers, and several species migrate long distances <5>. The Globe Skimmer is considered to be the most widespread dragonfly, occurring between the 40th parallels of latitude worldwide, and it is common across India <6>. Several populations of this species are known to migrate, and there are recorded migrations of Globe Skimmers from South America to Easter Island (possibly 3,600 km or more), to New Zealand (2,000 km), across the Chinese Bohai sea (nocturnal migrations) and over the Hindu Kush mountains (at altitudes of 6,500m asl). Within the Indian subcontinent, the Globe Skimmer arrives in Tamil Nadu after the North-East Monsoon, while in the western regions it arrives with the South-West monsoon, implying that there might be more than one migratory circuit even within this region.

While dragonflies and insects remain challenging to track over long distances, a number of studies have used arrival date information, mark-recapture techniques, and even radio-telemetry <7> to determine their migratory patterns. But, given the epic scale of the migration uncovered by Anderson, perhaps it would make sense to simultaneously examine both more visible taxa like birds and more populous taxa like insects. Doing so might provide a more comprehensive account of migratory patterns, mechanisms, and the evolutionary reasons for these spectacular journeys.

References

1. Anderson, R.C. 2009. Do dragonflies migrate across the western Indian Ocean? Journal of Tropical Ecology 25(4): 347-348. Download pdf.

2. The ITCZ is a weather system around the equator where the North-East and South-West trade winds converge. More information.

3. The ITZC in Africa. http://people.cas.sc.edu/carbone/modules/mods4car/africa-itcz/index.html

4. Meijing, L., Ke, F. and Huijun, W. 2008. Somali Jet Changes under the Global Warming. Acta Meterologica Sinica. 22 (4): 502-510. Download pdf.

5. Corbet, P. S. 1999. Dragonflies: Behavior and Ecology of Odonata. Cornell University Press, Ithaca.

6. Subramanian, K.A. 2005. Dragonflies and damselflies of peninsular India. A field guide. Edition 1.0. E-book of Project Lifescape, Centre for Ecological Sciences, Indian Institute of Science and Indian Academy of Sciences, Bangalore, India. 118 pages. Copyright K.A.Subramanian, 2005. Download pdf.

7. Wikelski, M., Moskowitz, D., Adelman, J.A., Cochran, J., Wilcove, D.S. and May. M.L. 2006. Simple rules guide dragonfly migration. Biology Letters, 2: 325-329. (Wikelski and colleagues radio-tagged 14 dragonflies in North America and followed them for 12 days with Cessna planes and ground teams.) Download pdf.