27 August 2016

Favourite Nectaring Plants #7

Butterflies' Favourite Nectaring Plants #7
The Spanish Needle (Bidens alba and Bidens pilosa)

In the 7th instalment of the series Butterflies' Favourite Nectaring plants, we feature an invasive weed that has become quite common in the wastelands and even cultivated gardens in Singapore. It is interesting to note that two or three decades ago, this plant (usually split into two different species) was largely unknown in Singapore. However, in recent years, it has somehow become quite widespread across the island.

An eight-petalled flower of the Spanish Needle

The plant that we are referring to, called the Spanish Needle (amongst a host of many other common names), is one of the favourite nectaring plants of butterflies. It is believed that there are two different species found in Singapore - Bidens pilosa and Bidens alba. The two species are almost indistiguishable in the field, and some botanists have lumped them as one species, whilst others believe they are hybrids of the same species. Due to their variability and existence of many hybrids for both species, we will, for all intents and purposes, deal with both species as a group in this article.

Plant Biodata :
Family : Asteraceae
Genus : Bidens
Species : pilosa and alba
Country of Origin : Tropical America
English Common Name : Shepherd's Needle, Spanish Needle, Romerillo, Common Beggarticks, Hairy Beggarticks, Cobbler's Pegs, Devil's Pitchforks, Black Jack.
Other Asian Names : 小白花鬼针, 鬼针草 (Chinese), 咸豐草 (Taiwanese), Ketul (Indonesia), Rumput Juala, Kancing Baju (Malaysia), Xuyến chi (Vietnamese), Pisau-pisau (Philippines), Ko-sendangusa (Japanese)

The debate amongst scientists and biologists continues regarding whether the two Bidens are distinct species or rolled into one. In the article by Robert Ballard in the American Journal of Botany Vol. 73, No. 10 (Oct., 1986), pp. 1452-1465, the separation of B. pilosa and B. alba was discussed and morphological differences explained. Generally, B. pilosa seeds have three to five barbs and B. alba has two or none. In addition, Wagner et al., 1999; pp. 279-281 proposed a key for the separation of the two species :
a) Ray florets 5-8 per head, rays 10-16 mm long: Bidens alba
b) Ray florets absent or 4-7 per head, rays 2-8 mm long: Bidens pilosa.

Top : Flower Bud of the Spanish Needle 
Middle : Flower of the Spanish Needle 
Bottom : Developing fruits of the Spanish Needle

As of January 2012, the United States Department of Agriculture (USDA) plants database continued to maintain the separation of species, but the Integrated Taxonomic Information System (along with the Flora of North America) has adopted a more recent classification which rolls B. alba and B. odorata into B. pilosa. Whilst the scientists continue to lump or split the two species, let us take a look at this weed and how it affects butterfly populations in Singapore.

A pristine flower of the Spanish Needle

Bidens pilosa/alba is an annual herb that grows erect up to about 1.5 m in height . It is easily recognised by white petalled flowers with a central yellow disc florets. The elongated fruits are bristly achenes (one-seeded fruits) with mainly 2-5 awns (barbed hooks) at tip. The fruits are black when mature, sticking onto fur or feathers and dispersed by browsing fauna via their hooked bristles that embed themselves in people's clothing as they brush past the stems.

Two fruits/seeds of the Spanish Needle.  Note the top fruits have only two awns (barbs) whilst the bottom shot shows the fruits with three awns.

The genus name Bidens means twice' (bi) and 'toothed' (dens), which probably refers to the hooked fruits of the plant. The leaves of the Spanish Needle are oppositely arranged and pinnate in form with three to five dentate, ovate-to-lanceolate leaflets. The leaf edges are serrated/toothed. The petioles are slightly winged. Stems are mostly hairless and green to purplish in colour.

The green serrated leaves of the Spanish Needle.  The bottom shot shows young leaves growing from the stem.

That the Spanish Needle is often referred to as a weed is testament to its tenacity and robustness in surviving in harsh environments. It is a fast-growing, fast-spreading weed due to its enormous number of seeds and the ability to re-grow from stems. It can have up to 6,000 seeds per plant and the seeds can remain viable up to five years.

Young shoots of the Spanish Needle can be brewed as a tea

The plant itself is edible, and the young leaves can be consumed as a vegetable. The young shoots and leaves can be added raw to salads whilst the shoot tips can be brewed as a tea. Almost two hundred compounds have been isolated from the Spanish Needle, especially polyacetylenes and flavonoids. The plant contains the chalcone okanin and ethyl caffeate, a hydroxycinnamic acid. It is considered a medicinal plant in many cultures and is used to treat ailments from minor fresh wounds and ulcers, to treat thrush and rheumatism. It is also used in enemas for intestinal ailments.

The flowers contain a high amount of nectar, and a wide variety of butterflies is attracted to feed on the flowers. It is interesting to note that the size of the butterfly and length of its proboscis do not appear to be critical to the butterflies' ability to feed on the Spanish Needle. We have observed a good range of butterfly species from the large Papilionidae to the diminutive Lycaenidae and the speedy Hesperiidae feeding on the flowers of the Spanish Needle.

Papilionidae feeding on the flower of the Spanish Needle

Amongst the Swallowtails, the larger butterflies like the Common Mormon, Common Mime and Banded Swallowtail have been observed feeding on the Spanish Needle flowers. The long proboscis of the Swallowtails can be observed as these large butterflies balance on the flower whilst still in flight with their forewings flapping whilst their hindwings are used to counterbalance the butterfly as it feeds.

Crows and Tigers feasting on the flowers of the Spanish Needle

The large slow flying Tigers and Crows also feed on the flowers of the Spanish Needle - the weight of the butterfly often pulling down the flowers as they stop to feed with their wings folded shut. Unlike the Swallowtails, the Danainae butterflies stop completely and hold on to the flower whilst feeding.

A wide variety of Nymphalidae and Pieridae on the flowers of the Spanish Needle

Amongst the Nymphalidae, a wide variety of the large and medium sized butterflies have been seen feeding on the flowers of the Spanish Needle. The Pieridae also take very well to the flowers of this high-nectar plant whenever available.

Hairstreaks and Skippers also love the flowers of the Spanish Needle

Even the small Lycaenidae love the flowers of the Spanish Needle, stopping and feeding for long periods of time, probing their proboscis into each floret for the energy-giving nectar. The speedy Skippers also join in on the flowers of this plant, angling their long proboscis into the flower.

Although considered a weed by urban landscape designers and parks managers, the Spanish Needle is one of the all-time favourite nectaring plants for butterflies, and whenever you encounter a field of this plant with the pretty white/yellow flowers in full bloom, you can be sure that there are butterflies nearby, waiting to feed on the nectar that these flowers produce.

Text by Khew SK : Photos by Sunny Chir, Khew SK, Loke PF, Simon Sng, Jonathan Soong and Horace Tan

References :

21 August 2016

Butterfly Photography at Our Local Parks - Upper Seletar Reservoir Park

Butterfly Photography at Our Local Parks
Featuring : Upper Seletar Reservoir Park

The pavilions at Carpark 'B' - a good starting point for your exploration of Upper Seletar Reservoir Park's biodiversity

In this weekend's article about butterfly photography at Singapore's local parks, we feature a nature park that is on the banks of our Upper Seletar Reservoir. This park, called Upper Seletar Reservoir Park, is also immediately adjacent to Central Catchment Nature Reserve and is more heavily forested than the usual urban parks that we have featured in this series. The 9-hole, Par 29 Mandai Executive Golf Course and Driving Range is also next to this park.

Lush forest edge greenery

Upper Seletar Reservoir Park covers about 15 Hectares of natural vegetation and is less heavily landscaped than a typical urban park. Where external planting is added to the area, these are minimal and the species selected appear to be more compatible with the nature reserves, where more native species are planted. The larger part of the park is left in its natural "wild" state with primary and secondary forest plants dominating the whole area.

Tranquil views of the Upper Seletar Reservoir

The Upper Seletar Reservoir, Singapore's 3rd impounding reservoir, (previously called the Seletar Reservoir), was built in 1920 and finally completed, after some upgrades in 1940. It was officially opened by Princess Alexandra of England in August 1969.

The landmark rocket-shaped tower at Upper Seletar Reservoir Park. It is now a nationally-conserved structure for its heritage value.
Left : As it looks today. Right : On the opening day in 1969. © National Library Board and Dr Chua Ai Lin

A rocket-shaped tower was designed by Singapore's Public Works Department (PWD) and completed that year, in time for the grand opening of the reservoir. The 18m tall, six-storey iconic tower was a favourite with Singaporeans during that period. It was given conservation status in 2009 by the Urban Redevelopment Authority (URA).

Access to Upper Seletar Reservoir Park can be quite inconvenient for non-drivers, although there is a bus service (Service 138) that stops along Mandai Road and it's a short walk to the nature areas from the bus stop. The first stop of interest to butterfly watchers starts at the two pavilions at Carpark B. From here, there is a short forest trail immediately behind the toilet block leading towards Mandai Road Track 7.

The Syzygium trees bordering Car Park 'B' are active with butterflies when they are in full bloom

The forest vegetation immediately behind the pavilions can also be good for butterflies, particularly when the Syzygium trees flower. Many rare forest species can then be spotted feeding on the flowers. At other times, one needs to be patient and observe quietly for species like the Purple Duke, Malayan Lascar and a number of Oakblues (Arhopala spp.) that will appear in the undergrowth from time to time.

Along the heavily-shaded forest trails, look for the ground feeders like the Yellow Archduke, Dark Blue Jungle Glory and Common Faun

Inside the forest trail, there are also opportunities to observe many different forest-dependent species that one will not often find in urban parks and gardens. Due to the variety of forest host plants, many species of butterflies that are associated with these plants can be found here. In the shaded understorey of the forested areas, look out for the ground feeders like the Archdukes, Common Faun, Saturn and Dark Blue Jungle Glory.

The 'dead-end' roundabout at Car Park 'C' near the NCC canoe shed.  The Green Oakblue occasionally makes its appearance here

Across from Mandai Road Track 7, the forest trail continues into an elbowed track and leads out to the other side of the road and to the roundabout "dead end" where the National Cadet Corps' canoe shed is. That area is also often a good hunting ground for butterfly watchers. Note that access beyond that area is not permitted and one chooses to wander beyond the out-of-bounds limits at their own risk.  Please comply with the 'no-trespassing' signs by MINDEF and NParks.

There are ample rain shelters around the park to take refuge in, or just for a short break

As many species of butterflies like to fly around forest edges, the open areas fronting the lush vegetation are often good places to wait for butterflies to appear. Areas where there are flowering plants like the Ixora bushes, and even the wildflowers like Asystasia or Elephant's Foot are worth exploring. The invasive creeper, Smilax bracteata, a bane of parks managers, is also useful in that it is the host plant of two small Lycaenidae - Branded Imperial and Yamfly. Expect to see these two species in the forested areas.

There are several rare Palm-feeding Skippers to be found along the trails of USR

Due to the large numbers of different species of Palmae, Poaceae and Arecacae, there are many Hesperiidae and Satyrinae that can be found in the vicinity. The variety of parasitic plants that occur on the mature trees will also play host to a number of rare Lycaenidae, and indeed, the occasional sightings of such species will always make a trip to such nature parks worthwhile!

Do watch out for aggressive macaques around the park.  Do not feed them and avoid any confrontations with them

As in any "wild" nature areas, be prepared for mosquito bites, the occasional bee/wasp sting, ticks (more recently, due to the presence of wild boars), snakes, centipedes and aggressive Long-Tailed Macaques. There are several troops of the macaques in the area, foraging for food, and human-macaque interactions in recent years have made them familiar with the food that comes with the "hairless monkeys". There have been regular reports of these macaques snatching food (or anything that looks edible) from visitors to the nature park.

USR is also a great place for other creatures and there is always plenty to amaze you

Besides butterflies, Upper Seletar Reservoir Park (codenamed "USR") is a hotbed of biodiversity, with many other taxonomic groups also recording a wide variety of species. Birders have often spotted rarities in the area and it is not surprising to see bird photographers with their big guns crowding the narrow trails of USR whenever a rare sighting is shared across the online groups.

The Plane, a rare Lycaenid that regularly makes an appearance at USR.
Top : Male ; Bottom : Female

Remember that this is a nature area and do not collect, damage or harm any of the biodiversity that you come across. Upper Seletar Reservoir Park has a lot to offer in terms of its flora and fauna, and it is hoped that the park will remain as a biodiversity haven for many years to come, so that different stakeholders can continue to enjoy the park.

How to Get There :
By MRT/Bus : Nearest current MRT is Khatib Bongsu, and thereafter by bus to Mandai Road. A future MRT station is being constructed near Springleaf area along Upper Thomson Road. Bus service No. 138 will stop just outside Upper Seletar Reservoir Park along Mandai Road.

By Car : See map for details. Park at Car Park 'B' and look for the pavilions as a starting point. Alternatively, park at the car parks along Mandai Road Track 7 towards the dead end near the toilet block adjacent to the NCC canoe shed. Car parking is free.

Text by Khew SK : Photos by Khew SK and Loke PF