Aquatic plants and other cover

Different aquatic plants have different values to waterfowl, as well as those which they all share. For example, all plants provide a nutrient and energy input to the water when, on death in the autumn, the plant tissue enters the water and decays, thus the water plants are the beginnings of the food chains which end in the desired quarry species, be it fish, fowl or both. Selective planting and management of the vegetation, should encourage a variety of different species for particular functions. For example the sea club-rush, great pond sedge and bur-reed all produce food for ducks in the form of seeds, and while bur-reed dies down in the winter and disappears, the dead stems and leaves of the sedge and club-rush remain standing until spring providing valuable winter cover and shelter. Dense beds of emergent reeds of almost any species are of special value as escape. Cover and shelter when the ducks are in full wing moult.

The submerged parts of all aquatic plants provide a 'scaffold' on which the insect larvae, worms, snails, water boatmen etc., find cover and food. Some of our research has shown that the plants which grow most densely, such as the seders, hold large numbers of animals of a wide range of species, while plants of less dense habit, such as the common reed, harbour fewer animals of a smaller range of species. This is apparently related to food and cover - the more dense the stems, the greater the surface area of plant available and therefore the greater the food supply and shelter that the plant affords. The densely growing sedges, club-rush, bur-reed and reed-grasses therefore hold more items of food for waterfowl.

The totally submerged plants, and those with some parts floating or emergent (of which the more important are the yellow and white water lilies, amphibious bistort, broad-leaved pond-weed, milfoil, crowfoots, stalwart, sago pond-weed, and some other fine leafed Potamogeton species) are probably more important than wholly emergent plants for the provision of shelter and food for invertebrates. These too can be introduced and planted where suitable.

Site preparation and planting for habitat improvement

The factors to consider when embarking on a planting programme are the nature of the water body and the selection of species that suit both the conditions and any specific requirements. First of all, the existing vegetation should be surveyed at flowering time when identification is easiest using simple field guides. This will avoid the chance of planting species that are already present, and will facilitate planning any additions or removals. Similarly, it is advisable to identify a source of transplant material at flowering time, and mark the position carefully so that selected plants can be taken at the appropriate time.

The water quality and nature and profile of the bed of the lake are also important. Mineral-poor waters over hard sand or gravel, or acid peaky waters, will not encourage plant growth and may need treatment with topsoil, fertiliser or lime to improve them. The growth of plants in waters on sterile soils can often be improved by the addition of fertiliser and 6-8-4 NPK is suitable if enriched with either ammonium sulphate for hard water or nitrate of soda for soft water to give an 8-8-4 mixture. It should be applied in nine or ten 'doses', each of about 1 cwt. (50 kg.) per hectare. The first application may be made in April or May, and followed each week by another for a period of six weeks and then monthly until the autumn. The fertiliser should be broadcast from the windward shore on a breezy day and some should be spread on the margins to promote the growth of fringe plants. Waters with high calcium content are normally best for plant growth and for invertebrates and fish, and should present no problems. Clay beds suit a wide range of plants, provided the clay does not cloud the water. Depths of more than 13-15 ft. (4-5 m.) will probably restrict growth or eliminate most water plants. The margins and shallows are therefore the best places to consider for planting, remembering of course to leave suitable open loafing areas, preferably on S. or S.E. facing island shores. In the case of deep lakes or wet gravel pits, it is often wiser to dig out shallow lagoons or wet shelves around the margin rather than attempt to establish plants in deep water. In small ponds it is a good plan to extend the shoreline by digging bays into the banks. The size of the duck population is governed more by the length and suitability of the shoreline than the area of water. Sources of material and planting techniques

The way to guarantee success in planting is to introduce species that grow well in local natural water bodies. Invasive plants such as common reed and reedmace should be planted only where their growth is restricted by local conditions e.g., on a ridge surrounded by deep water or on a marginal shelf. Each species should be planted in a group occupying a stretch of shoreline sufficient in area to ensure it becomes firmly established before meeting competition from a neighbouring, perhaps more vigorous species.

Very shallow water, i.e., less than 12 in. (30 cm.) deep should be planted with low-growing marsh plants such as common spike-rush, brook-lime, mare's-tail etc., which are easy to control and which are good low cover for ducklings and waders

The most productive zone is invariably the interface between two different stands of vegetation or between vegetation and open water. Here, water and nutrients circulate freely, light can penetrate, and invertebrates have easy access, as do fish and ducks. It is important, then, to create as much 'edge' as possible during planting. Most emergent reeds tend to form pure stands, and several small blocks of different species along a shore is much preferred to a few large stands of any one species. For instance, in some species the stems are so dense that ducklings and fish can only feed around their edge. For this reason the pattern to be aimed at is a number of groups of these high-production species in a matrix of less dense types such as reedmace, common reed, flag iris, bulrush etc., which allow access for feeding ducklings and fish. When collecting transplant material, treat it with care. Keep the roots wet and re-plant as soon as possible in the new site. Simply lift a small piece of rhizome or root of the plant by pulling or digging, in some cases taking the whole plant if it is small, and heel in the pieces in the required place. Rhizomes are best collected at the end of the plants' dormant period in spring, just as the new shoots appear. A piece taken with a growing tip will establish best. Autumn planting does work, but with a lower success rate and many plants will wash out over winter. If autumn planting is necessary, cover the material well with soil or a stone, or hold it down with a wire arch, and remove all top growth to prevent swans and coots uprooting the plants. If there is a large swan or coot population, the plantings must be protected until they are established. Whatever the time of year, plantings on exposed shores will need protection with floating pole baffles to reduce wave action and erosion. If a current is flowing, plant in 4-in. (10 cm.) deep trenches and place stones on the top. If other species are found to be mixed with the selected transplants, leave them in, and they will add to the diversity; undesirable species should, of course, be removed. The non-rhizomatous plants that will transplant readily include most of the submerged ones, plus watercress, brooklime, great water dock, marsh marigold and stalwart. Watercress grows well from seed, but the others need to be dug with a good root ball in late spring or early summer when growth is vigorous before flowering. Cuttings of milfoil and crowfoot can be pushed into the mud in shallow water, or into a clay ball which is sunk in deeper water, and the leafy tips of many submerged species, especially of the Potamogeton pond-weeds, can simply be thrown into water where they will put out roots, but this is wasteful of material as success rate is not high and there is no control over where the plant grows.

Some useful food plants such as arrowhead, broad-leaved and sago pond-weed produce tubers or winter-buds called turions as over-wintering stages, and these can be collected in autumn for broadcasting in the water, or they can be stuck in clay balls and sunk in selected spots.

Most submerged and floating-leafed plants should be introduced into 3-6 ft. ( 1-2 m.) of water, preferably on a soft lake bottom, while the emergent plants should not go into more than 3 ft. (1 m.) of water.

Plants that are useful to waterfowl can be considered in several groups:

a. Plants which are totally submerged or which have only their flowers, and perhaps a few leaves, above the water surface.

b. Free-floating plants.

c. Emergent plants that have leaves floating on the water surface.

d. Emergent (marginal) plants that have erect leaves held above the water surface.

e. Marsh plants.

f. Terrestrial plants giving ground cover and/or food. E.g. Trees and shrubs giving shelter and food.

There is necessarily some overlap between these groupings, but they form a broad basis for clarification.

(a) Totally submerged plants with only their flowers and perhaps a few leaves above the water surface

Ranunculus aquatilis. Will grow in swift streams or ponds, sometimes in moderately acid water.

Ranunculus baudotii. Coastal areas in brackish streams, ditches and ponds. The seeds of Ranunculus species often mature in early summer and their value may be higher than suggested by studies done during the shooting season.

A common plant on mud in shallow water. Ranunculus circinatus. A locally common plant in ditches, canals, ponds, gravel pits and lakes with a high mineral content. Tassel pond-weed (Ruppia maritima). The American name for this coastal plant is widgeon-grass. It grows on bottoms of fertile soil or sand in depths of a few inches to several feet. The seeds are eaten by mallard and other dabbling ducks. Chara spp. An abundant plant in still and slow-running water. Much favoured by pochard and teal. Elodea canadensis. A widespread submerged aquatic plant that can grow to a depth of 12 ft. (4 m.). It will often choke a pond to the exclusion of other species and then almost die away. The male plant is very rare in the British Isles and so seed production is usually nil. It does, however, 'carry a very rich fauna of wildfowl food animals including the Jenkins' pire shell which is an important food for young a d adult tufted duck. This plant can be a great nuisance to fishermen because of its invasive habit. It can, however, be controlled reasonably effectively and safely with Horned pondzweed (Zannichellia palustris). This is a slender, short species reaching a length of approximately 18 in. (45 cm.). Its seeds are eaten and it lives in fresh or brackish water.

Fennel-leafed (Potamogeton pectinatus). Grows in ponds, ditches, canals, rivers etc. Its seeds and tuberised lateral rhizome buds are eaten. It particularly likes alkaline water.

(b) Free-floating plants

* Duckreeds. All are eagerly taken by wildfowl. Lesser duckweed, the commonest species, is found floating in all types of still water, often covering the surface. Thick duckweed, ivy-leaved duckweed - submerged species except in the height of summer. Value to wildfowl is fair to excellent. Ivy-leaved duckweed thrives best in moderately acid waters and lesser duckweed is also said to be best in slightly acid water, but tolerates a greater rarye than other duckweed.

Frog-bit (Hydrocharis morsus-ranae). This is a floating aquatic perennial with thick kidney-shaped leaves, about 4-2 in. (2-5 cm.) across. It rarely produces seeds in this country, but is useful for the food animals that it harbours. It is somewhat local in distribution, being found in ponds and ditches in calcareous districts where it can sometimes be common. (c) Emergent plants which have leaves floating on the water surface. This is common in lakes, ponds and ditches. Its seeds and roots are eaten by wildfowl. It lives in depths from 12 in. (30 cm.) to 42 ft. (12'- m.) but is usually found in shallow water less than 3 ft. (1 m.) deep and tolerates acid waters, favouring a highlv organic substratum.

**Amphibious A widespread and common plant that grows a good crop of seed and makes excellent surface cover for ducklings, which conceal themselves in the emergent flower stalks. flowers arc scented and attract flying insects which provide food for the ducklings. It has a terrestrial form which lives on banks by water, growing between 12 in. (30 cm.) and 29 in. (74 cm.) high. Large mats of bistort floating on the surface of a lake have a very marked damping effect on save action.

(d) Emergent plants which have erect leaves held above the water surface

in height. It penetrates and spreads by means of small tubers called turions. These are readily eaten by wildfowl. It is characteristic of muddy substrata and grows best in shallow water about 6in. ( 1 5 cm.) deep. The foliage proves good cover for ducklings, but it dies down quickly after the first frosts. A similar species in the United States is called the `duck potato'.

* Gover plant, locally common in ponds, lakes and slow streams. On one breeding area that we visit regularly the emergent tips are often infested with blackfly, which provide very good food for ducklings. The seeds are also eaten by ducks. It can withstand moderately alkaline and moderately acid conditions.

**Bur-reed, Food and cover plant. Common and widespread by rivers, canals and ponds and has proved very successful on some gravel pits. It grows on mud and in shallow water, producing a crop of seeds. Spring planting of divisions is recommended. It is invasive of water up to 18 in. (46 cm.) deep in many favourable locations. Three closely related species are good food and cover plants for wildfowl.

*Common spike-rush. Provides seed for wildfowl and is found in wet meadows, marshes, ditches and the margins of ponds. It grows in dense tufts 6-12 in. (15-30 cm.) in height. Favoured by teal.

* Common bulrush. Found in the margins of rivers, lakes and ponds, usually where there is an abundance of silt. It grows 6-72 ft. (2-22 m.) and its seeds are eaten by mallard and teal. (This species should not be confused with reedmace, which is commonly called `bulrush'.) It seems to be less common in Wales than other parts of the British Isles. It can be invasive.

Reedmace (Typha latifolia). The false bulrush. This is an invasive plant, not of much direct value to wildfowl, although the analysis of the stomach contents of ducklings collected from amongst stands of reedmace has shown that it can harbour much in the way of insect foods. It is often dominant, especially on inorganic substrate such as the bottom of newly dug gravel pits or where there is silting and rapid decay of organic matter. It is not usually advisable to plant reedmace unless at least 80 per cent of the area is more than 3 ft. (1 m.) deep. Its distinctive cigar shaped seed head distinguishes it from the true bulrush.

Hair sedge, hammer sedge (Carex hirta). Commonly found in damp grass and near ponds. The seeds are eaten by mallard and propagation is by division. *Lesser pond sedge (Carex acutiformis) and greater pond sedge (Carex riparia).

Common in the fringes of still or slow-moving freshwater or round ponds. Their seeds are eaten by mallard. They provide early cover.

Flote-grass or Manna grass (Glyceria fluitans) . Growing from 6 in. (15 cm.) to 2 ft. (60 cm.) high and is common in stagnant or slow-flowing shallow water throughout the British Isles. The seeds, freshly produced, are readily eaten by wildfowl. Propagation is by seeds and by division.

Reed-grass (Glyceria maxima). A taller 3-6 ft. ( 1-2 m.) grass growing in similar situation to flote-grass but often in deeper water. Abundant beside most lowland rivers but becoming rare in Scotland. Seeds eaten by mallard. This species is highly invasive of shallow water, forming a very dense stand through which ducklings might find it hard to travel.

**Sea club-rush (Scirpus maritimus). This plant has been proved to be a very important source of food for mallard during the winter in brackish-water areas where it is locally abundant in ditches, ponds and rivers. We have been successful in establishing it in alkaline-water gravel pits by means of division. It appears not to be invasive.

Common reed. A stout, erect reed growing to a height of 9 ft. (3 m.). It stands upright throughout the winter. It is very widely distributed in swamps and shallow water, but is absent from extremely poor and acid habitats. It provides winter cover and wind shelter, and is useful in preventing bank erosion in the most exposed places.

(e) Marsh plants

Great dock (Rumex hydrolapathum). This stout perennial (3-6 ft. [ 1-2 m.]) is found in wet places beside and in ponds, lakes, streams, etc. Propagated readily by seed or division. The seeds are eaten by duck. The seeds of other dock species are also very important wildfowl foods.

* Creeping buttercup (Ranunculus repens) . Typically found on heavy soils and in wet meadows, by rivers and ditches. The seeds are eaten by mallard and teal.

Waterpepper (Polygonum hydropiper). Sometimes useful, being found commonly in marshy fields and in shallow water on the edge of ponds and ditches. Mallard eat the seeds.

(f ) Terrestrial plants

Persicaria, redleg or redshank, black knotgrass, fat hen, common orache. All these weeds are widely found on disturbed ground, arable land and the banks of ponds and rivers. They are all free seed producers over much of the year and the seeds are readily eaten by foraging duck.

Blackberry or bramble (Rubus fruticosus). The pips are eaten by duck and this is one of the best natural cover plants.

Summary For those who are in doubt and wish to keep things simple, the three groups of useful plants which are available in most ponds and streams are:

1. Tall reed cover (bur-reed, reed grass)

2. Low marginal cover (common spike rush, brooklime, yellow cress) 3. Emergent plants (broad-leaved pondweed, amphibious bistort) Game Conservancy research on wildfowl production

As this book explains, the techniques for improving wetland habitats to increase the breeding populations of waterfowl are well understood and are relatively easy to apply. There are, however, problems such as the low fledgling success rate of ducks breeding on many gravel pits. The production of young mallard can be very low due to an extremely high mortality rate early in life. This is just one of the areas of study covered by our research programme.

The study of wild duck breeding biology was intensified in 1979, the aim being to produce a reliable mathematical population model which can be used to predict the effects of variation in several important factors (such as weather, predation, food supply etc.) on the breeding success of mallard and tufted duck at different population densities. This will be an extremely valuable tool for management of waterfowl populations - for example, showing the cost -effectiveness of predator control programmes, and indicating the proportion of a population that could be shot without adverse effect.

One of the early projects undertaken was a study of the food taken by adult mallard. This emphasised the dependence of inland mallard on the farming pattern of the surrounding area for their food supplies in late summer, autumn and winter. At these times 90 per cent of the food of mallard in our study area is of agricultural origin. Cereal grains, mainly barley but including some wheat and oats, are taken from laid crops as early as July. However, most of the cereals taken are spilled grains, gleaned from stubbles after the harvest. This enormous food resource can enable the birds to build up their body fat reserves and the assessment of the conditions of shot birds shows a very significant increase in body weight and size of fat deposits over the autumn and early winter. The general condition and amount of body fat begins to decline in February and March - the time when food supplies are scarce. The investigation shows that the local pattern of agriculture should be considered in any plans to develop a breeding reserve for mallard. Success will obviously be easier to achieve in extensive cereal growing areas.

The study of the feeding ecology of the adult mallard was extended to examine the food taken in spring and summer. There is a change from a predominantly plant diet to one consisting chiefly of invertebrates, including many aquatic species. This change may reflect an increased need for animal protein for gametogenesis (reproduction) and feather replacement after the moult, and also the fact that there are fewer seeds and other plant foods available, the crop from the previous autumn having been eaten, dispersed, or germinated.

There is an obvious advantage to the species - juveniles and parents require the same foods. A parent bird which selects an insect-rich area in which to find food will also be choosing the right area for its brood and it has been shown that mallard with newly hatched broods, select the areas known to be richest in emerging midges. Diet investigations have revealed that the very young birds depend on an abundant supply of aerial insects in the first few days of life, and ducklings do much better in areas which are very rich in insect life. A well fed duckling, with a large part of its diet consisting of high-grade protein will grow faster, and be better able to cope with hazards such as poor weather, than ducklings made weak through lack of food of the necessary quality. An experimental feeding trial confirmed the hypothesis that for satisfactory growth, the ducklings needed invertebrate material in their diet.

The majority of the necessary aquatic invertebrates live on or amongst aquatic plants, or in the sediments of the lakebed. Most of them feed on algae or on dead and decaying organic matter (detritus), and in a new gravel pit, with no inflowing stream, the accumulation of detritus takes a long time. We have therefore developed a technique for the enrichment of the sediments of newly flooded gravel pits using straw. We have shown in a number of practical trials that the addition in spring of about 10 tonnes per hectare (1 kg. per square metre) of barley straw to a suitable lake, i.e. one with alkaline water and a non-organic sediment, significantly increases the amount of invertebrate life present on the bed of the lake. Eventually, when the straw has decayed, it stimulates the production of larger numbers of chironomid midges, which can then be exploited by the wildfowl. The increased production of aquatic invertebrates would, of course, also be of tremendous benefit to the fish in the water, which we believe may be in direct competition with waterfowl for these vital invertebrate food organisms.

Incidentally, we have noted that the addition of straw in spring also helps to reduce algal bloom problems and it will help to stabilise soft lake silts, speeding up colonisation by aquatic plants.

The knowledge gained from this study should enable us to create the conditions needed to ensure that ducklings produced by the wild duck attracted to areas such as our reserve have a better chance of reaching maturity.

In this way, breeding sanctuaries can be made to produce a surplus of wildfowl to improve the shooting potential of the surrounding area, and to replace those birds that are shot elsewhere. With the dramatic rate of loss of natural wetlands it is vitally important for the future well being of European waterfowl that we manage as many areas of existing and new man-made wetlands as possible so that they can harbour and produce wild waterfowl.

Conclusion To many of us there can be no more exciting sport than wildfowl shooting, and no more rewarding activity than the practical conservation that increases the shootable surplus and safeguards the breeding stock. We hope that this web page will stimulate readers to realise the importance of the improvement of wetland habitat. Even a small effort can have really worthwhile results in terms of increased wildfowl production and those who apply in any way possible some of the practical techniques outlined here can be assured that the rewards are well worth the effort.

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